What happens behind that "ding" sound? — An in-depth analysis of contactless payment technology

Introduction: That magical half-second

You've definitely had this experience: when checking out at a convenience store, you take out your phone or bank card, tap it lightly on the counter, and with a "ding," the payment is complete. The whole process takes less than half a second.

But have you ever wondered what exactly happens in that fleeting half-second? What kind of "conversation" takes place between your phone and that POS terminal? How is your bank card information transmitted, verified, and authorized? Why can this seemingly casual "touch" securely complete a transaction worth thousands or even tens of thousands of yuan?

This video will take you deep into the world of contactless payments. We'll start with the most basic principles of electromagnetic physics, explore encryption technologies and security architectures, examine market trends, and culminate in cutting-edge AI-powered payment agents and biometric cards. Whether you're a tech-savvy user or an industry professional looking to stay informed, you'll find the answers you're looking for here.

Physical layer: Why is it necessary to "touch" it?

The core technology for contactless payment is NFC (Near Field Communication). The name itself reveals a key piece of information: "near field".

NFC operates in the 13.56 MHz radio frequency band, a globally recognized industrial, scientific, and medical band. However, unlike Wi-Fi or Bluetooth, which we are familiar with, NFC does not rely on long-distance electromagnetic wave propagation. It operates in a "near-field region" dominated by magnetic induction —in this region, energy is primarily stored in the magnetic field rather than radiated outwards.

What does this mean? Simply put, if someone wanted to eavesdrop on your payment information from a distance, they would need an extremely sensitive device to detect even the slightest leaks in the magnetic field. This is far more difficult than eavesdropping on Wi-Fi signals, which are specifically designed for long-distance transmission.

From a physics perspective, a frequency of 13.56 MHz corresponds to a wavelength of approximately 22 meters, and, in theory, the near-field boundary could extend to about 3.5 meters. However, in practical payment applications, the effective working range is strictly limited to within 4 centimeters. This is not a helpless compromise due to technical limitations, but rather a deliberate security design.

Why? Because the 4-centimeter limit creates a "physical intent threshold ." You must consciously bring your phone close to the terminal to trigger a payment. This dramatically reduces the risk of accidental touches or passive payments. In other words, distance itself acts as a security barrier.

So, how is data transmitted within those mere 4 centimeters? There's a clever mechanism called "load modulation ." Traditional contactless bank cards don't have built-in batteries—they're completely passive. When you bring the card close to the reader, the reader's magnetic field induces a voltage on the card's antenna. This voltage, after rectification and regulation, powers the chip on the card.

When a card wants to send data to the reader, it changes the load impedance on the antenna coil. This change is detected by the reader's antenna via mutual inductance between the two coils and is interpreted as a data signal. The whole process is like two people communicating through a shared spring—if one pulls hard, the other feels the vibration.

The situation is slightly different for smartphones. Because phones have their own batteries, they can use a technique called "active load modulation ." The phone actively drives a reverse signal, ensuring reliable communication even with a smaller antenna than specialized equipment. This is especially important for SoftPOS (Software Point of Sale) technology—when an ordinary consumer's phone becomes a point-of-sale terminal, active load modulation guarantees sufficient communication range.

Transaction process: a seven-step protocol within 0.5 seconds.

The physical layer solves the problem of "how to transmit bits," but what do these bits represent? How to ensure transaction security? This is the responsibility of the EMV (Europay, Mastercard, Visa) specification.

The EMV specification transforms simple data exchange into secure financial transactions. It defines a rigorous seven-step protocol, each step incorporating cryptographic verification and risk assessment. Industry standards require the entire process to be completed within 500 milliseconds—that's the "ding" sound you hear.

Step 1: Application Selection. When your phone enters the terminal's magnetic field range, the terminal first needs to solve one problem: you may have several cards in your wallet, which one should you use? The terminal will issue a SELECT command, requesting the phone to return a list of supported payment applications. The phone might say, "I have a Visa credit card, a Mastercard debit card, and a UnionPay card." The terminal then compares this list with its supported options and selects the one with the highest priority.

Step 2: Obtaining Processing Options. After selecting an application, a specific "kernel" takes over. Each card organization (Visa, Mastercard, UnionPay, etc.) has its own kernel that defines unique transaction logic. The terminal sends a GPO (Get Processing Options) command to the phone, and the phone returns a "map" indicating which data should be read.

Step 3: Record Reading. Following this map, the terminal reads static data stored in the phone's security chip, including the primary account (PAN), card expiration date, issuing bank public key certificate, etc. This information is prepared for subsequent authentication.

Step 4: Offline Data Authentication. This is a crucial step in preventing card cloning. The terminal verifies a dynamic digital signature generated in real time by the card's chip. Even if an attacker copies all the card's static data (card number, expiration date, etc.), they cannot forge this signature because it requires a unique private key on the chip. State-of-the-art solutions (CDA, Combined Dynamic Authentication) also bind this signature to the subsequent transaction password, ensuring that the authenticated data is the actual transaction data.

Step 5: Cardholder Verification. The system needs to confirm whether the person holding this phone is the cardholder. For small transactions (e.g., under £100), this step may be skipped entirely. For large transactions, a PIN code or biometric verification is required. In Apple Pay and Google Wallet, this verification occurs the moment you unlock your phone—your Face ID or fingerprint serves as proof of your identity. This method is called CDCVM (Consumer Device Cardholder Verification Method).

Step 6: Terminal Risk Management. The terminal assesses transaction risk in accordance with internal rules. Does the amount exceed the limit? Is this card on a blocklist? Is the network connection regular? Based on these judgments, the terminal decides whether to authorize online (contact the bank) or approve offline.

Step 7: Password Generation. Finally, and most crucially, the card uses a unique symmetric key derived from the issuing bank's master key, combined with parameters such as the transaction amount, date, and a random number, to generate an Application Request Password (ARQC). This password acts like a unique digital fingerprint—the issuing bank can verify it using the same mathematical methods to confirm that it is a genuine card, the transaction details have not been tampered with, and the transaction occurred at the claimed time and place.

Seven steps, 500 milliseconds, dozens of encryption operations—this is the story behind the "ding" sound.

Bank cards and mobile wallets: the same technology, different philosophies

Before delving into mobile wallets, we shouldn't forget the "natives" of contactless payments—contactless bank cards. In fact, the bank card with the contactless payment logo (four curved lines) in your wallet uses the same NFC technology and EMV protocol as Apple Pay and Google Wallet on your phone. However, they have subtle but essential differences in their design philosophies.

Bank cards: Simplicity equals reliability

The most significant advantage of contactless bank cards is that they don't rely on batteries or operating systems. They have no battery, don't need charging, and don't depend on an operating system—as long as the card is physically intact. The terminal is working correctly, and transactions can be made. The moment you bring the card close to the reader, the reader's magnetic field powers the card's chip, and the transaction begins immediately. This passive design means that while you might not be able to enter the subway if your phone is out of power, your bank card is less likely to fail at the device level.

From a security perspective, bank card keys are stored in a secure chip inside the card, essentially the same technology as the Secure Element in a mobile phone. From the moment the chip leaves the factory, it encapsulates the private key written by the issuing bank. These keys are typically designed to be non-exportable, with the security goal of making copying or extraction extremely costly. Even if the card is stolen, it is tough for attackers to copy the keys within the chip for cloning.

Hierarchical logic for cardholder verification

However, bank cards also have a significant "inconvenience": they don't know who you are.

Mobile wallets can verify "whoever is holding the phone is the owner" through Face ID or fingerprint, but bank cards lack this capability. Therefore, bank cards employ a tiered verification strategy based on the amount held:

Small transactions (PIN-free payments): Many countries and regions have a limit on PIN-free payments (such as the current limit of £100 in the UK). Transactions below this amount can usually be completed with a simple tap. However, whether PIN verification is triggered is also affected by the card issuer's risk control rules. For example, verification may still be required after the cumulative amount or number of consecutive transactions reaches a threshold.

Large transactions (PIN verification): When the limit is exceeded, the terminal will prompt you to enter a 4-to 6-digit PIN. This is slower than Face ID, but it is more universal—any terminal supports it.

Cumulative spending limit protection: Even if each transaction is within the PIN-free range, the system will still require a PIN after multiple consecutive transactions to prevent the card from being repeatedly stolen and used fraudulently.

It's worth noting that the UK's FCA has announced that, from March 2026, it will give card issuers greater flexibility to set contactless payment limits. This means that future limits may vary from institution to institution, and may even allow users to set their own limits. However, this is not an "automatic removal of limits"—most institutions are expected to maintain their current caps in the short term. Coupled with the rise of biometric payment cards (cards with built-in fingerprint sensors), large-amount contactless payments will become more common in the future.

This design reflects a pragmatic trade-off: speed is prioritized for small transactions, while security is prioritized for large transactions.

Where is the "upgrade" for mobile wallets?

If bank cards are secure enough, why use a mobile wallet?

The answer lies in three aspects:

Tokenization protection: When you add a bank card to Apple Pay, your phone stores a "Device Account Number" instead of the actual card number (PAN). Even if this token is compromised, attackers cannot use it to shop on other devices or online. Physical bank card numbers are fixed, making them much more vulnerable if compromised.

Biometric integration: Before each payment, your phone has already verified your identity via Face ID or fingerprint. This means that mobile wallets can skip PIN entry while providing higher security than "no verification"—the best of both worlds.

Centralized management: If you lose your phone, you can remotely freeze all the cards linked to it; if you lose your bank card, you need to report each card as lost individually.

Their common foundation

Whether it's a bank card or a mobile wallet, the moment they "touch" the terminal, they all execute the same EMV seven-step protocol: application selection, obtaining processing options, record reading, offline data authentication, cardholder verification, terminal risk management, and password generation. Although the terminal can infer whether the other party is a physical card or a mobile wallet based on specific data characteristics (such as AID, CVM results, etc.), regardless of the form, it will complete the encrypted communication using the same standardized EMV process.

This is precisely the elegance of NFC payments: the same infrastructure serves both the simplest plastic cards and the most advanced smartphones. You can choose the most suitable tool for the situation—bank cards are always reliable, and smartphones are more intelligent.

Security Architecture: Apple and Google's Different Choices

When EMV credentials were transferred from plastic cards to mobile phones, a fundamental question arose: where should the encryption keys be stored?

This issue has given rise to two drastically different security philosophies. Apple and Samsung opted for the Secure Element (SE) model, while Google pursued Host Card Emulation (HCE). Each choice has its advantages and disadvantages, profoundly impacting the security landscape of mobile payments.

Security Elements: Bank-Grade Hardware Fortress

The Secure Element is a tamper-resistant chip embedded in iPhones and Samsung phones. It is completely isolated from the central processor and operating system — it has its own secure operating system, independent memory, and a cryptographic coprocessor. You can think of it as a miniature vault installed in your phone.

When you add a bank card to Apple Pay, the bank generates a unique Device Account Number and writes it directly to this secure chip. From that moment on, the iOS system—not even Apple itself—cannot read this key. When you make a payment, iOS can only "request" the secure element to sign the transaction, then receive the cryptographic authorization signal returned.

The security advantage of this architecture is absolute. Even if your iPhone is jailbroken or malware gains root privileges, attackers cannot extract keys from the secure element. This is why Apple Pay is considered the most secure solution for mobile payments.

Host card emulation: The cost of flexibility

Google faced a different dilemma. In early Android phones, the Secure Element was often embedded in the SIM card and controlled by the mobile operator. Google didn't want to be controlled by the operator, so it took a different approach: HCE technology allowed the NFC controller to route data directly to the Android central operating system, bypassing the Secure Element.

However, this presents a fundamental security challenge: the Android operating system is a general-purpose computing environment that is theoretically vulnerable to malware. Storing long-term keys in such an environment is dangerous.

Google's solution is tokenization and time-limited keys (LUKs). Google Wallet doesn't store your real card number; instead, it stores a series of "one-time" keys, each valid only for a short period or a limited number of transactions. When these keys are exhausted or expire, the phone needs to connect to the Google cloud to obtain new ones.

The advantage of this design is its flexibility and openness, without relying on specific hardware. However, the trade-off is that payments will fail if your phone is offline for too long, and malware with Android root privileges could intercept these temporary keys.

To compensate for this weakness, modern Android devices typically use a Trusted Execution Environment (TEE) —a physically isolated region within the central processor—to handle HCE logic. This is a compromise between pure software and complete hardware isolation.

The choice between these two models reflects the perpetual tension between security and openness. Apple opted for a "closed but unbreakable" approach, while Google chose an "open approach requiring additional protection ." For the average user, both are secure enough—the genuine concern lies in the new attack methods discussed in the next section.

Threats and Protection: An Arms Race Between Security Architects and Criminal Groups

As more and more funds flow through NFC channels, attack methods are also constantly evolving. The "Ghost Tap" attack that emerged at the end of 2024 raised the industry's level of vigilance to a new level.

Relay attack: turning 4 centimeters into 4,000 kilometers

Remember when we said that the NFC's 4-centimeter working distance is a security barrier? The purpose of a relay attack is to break through this barrier.

The attackers used two devices: a "mouse" device placed near the victim's bank card or mobile phone, and a "proxy" device placed near a remote payment terminal. These two devices were connected via a high-speed network (Wi-Fi or 5G) to relay ISO 14443 commands in real time. From the payment terminal's perspective, it "saw" a bank card right in front of it—even though the actual card might be thousands of miles away.

Ghost Payment: A More Covert Evolution

"Ghost payments" are an upgraded version of relay attacks. Attackers first steal victims' bank card credentials through phishing or malware, then link these credentials to Google Pay or Apple Pay on their own devices. Because the transactions originate from a "legitimate" wallet and generate a valid ARQC password, traditional fraud detection systems often fail to detect the anomaly.

Researchers have discovered that in 2024, more than 760 malicious Android applications exploited NFC permissions to launch attacks. These applications can simulate card readers to steal data from physical cards, simulate bank cards to make unauthorized payments, and even trick users into entering PIN codes by overlaying them onto the interface.

Distance Limiting Protocol: Combating Fraud with the Laws of Physics

The industry's response is a distance-limiting protocol. This protocol measures the round-trip time (RTT) of a signal with nanosecond precision. Since the speed of light is constant, any signal relayed through the network introduces additional latency—even a few milliseconds—which can cause the RTT to exceed the threshold, triggering a transaction rejection.

Implementing this protocol requires adding new hardware capabilities to the device and card/wallet. These upgrades are being rolled out gradually throughout the 2025-2026 update cycle. Meanwhile, AI-driven behavioral analytics (such as device fingerprint recognition and detection of impossible geographic movement speeds) are becoming an essential supplementary defense.

Security is never a one-time solution. It is a never-ending arms race—every evolution of attack methods drives the upgrading of defense technologies.

Public Transportation: A Touchstone for NFC Technology

The "tap-to-pay" feature at convenience stores is an everyday application of NFC payments; public transportation systems represent its ultimate stress test.

Imagine subway turnstiles during rush hour: processing 40 to 50 people per minute. This means the response time for each "tap" must be under 300 milliseconds—more stringent than the 500-millisecond standard in retail scenarios. Subway network environments are often unstable, requiring the system to support batch clearing after offline transactions. Adding to the complexity, unlike supermarkets, the system doesn't know the final fare when a passenger enters—you might ride one stop or all the way to the final destination. This necessitates a "swipe card upon entry/swipe card upon exit" mechanism to calculate the actual journey.

It is precisely these stringent requirements that make transportation systems a frontier for NFC technology innovation.

Comparison of major global transportation payment systems

system	area	Technical features	Innovation
Oyster + Contactless	London	Open EMV and proprietary Oyster card in parallel	The first concept of "ticket price cap"
Suica / PASMO	Japan	FeliCa (Sony proprietary agreement)	0.1-second ultra-fast response; supports payment even when the device is powered off.
Octopus	Hongkong	FeliCa variant	From transportation to convenience stores and parking lots
SimplyGo	Singapore	Migrating from CEPAS to Open EMV	Complete the full open payment transformation by 2024
OMNY	New York	Purely open EMV	No dedicated card, relies entirely on bank cards/mobile wallets

The Metropolitan Transportation Authority (MTA)'s OMNY system represents the latest development. It completely abandons proprietary cards, accepting only open bank cards and mobile wallets. Even more innovative is its "fare cap" mechanism: for example, after 12 swipes within a week, the remaining trips are free. This logic isn't stored on the card; it's calculated in the backend based on your unique payment token—the system "recognizes" you without requiring you to register an account.

The traditional MetroCard ceased sales on December 31, 2025. On January 4, 2026, Westchester County's Bee-Line transit system also fully adopted OMNY, creating a seamless payment zone in New York City and its northern suburbs.

It's worth noting Japan's Suica/PASMO system. It uses Sony's FeliCa protocol—not strictly part of the ISO 14443 standard—but offers an astonishing 0.1-second response time. More importantly, it supports payments even when the device is powered off.

This raises a question that many people are concerned about: If your phone is out of battery, can you still use your card to enter the subway?

Payment when powered off: When the battery is depleted

The answer is: It depends on the device you are using and the situation.

iPhone: Some models are available.

Starting with iOS 12, Apple introduced the "Power Reserve" feature. When your iPhone battery is depleted or you manually shut down your iPhone, your Express Transit card can still be used for up to 5 hours.

How is this possible? Remember the Safety Element? It's a separate chip with its own low-power circuitry and small capacitors. When the central system is shut down, the Safety Element can operate independently—like a miniature "backup power supply."

Please note: This feature is limited to transit cards (such as Suica, OMNY, Beijing/Shanghai transit cards). Regular credit card payments—such as buying items at a convenience store—require Face ID verification, which cannot be performed when the device is powered off. You will need to enable the "Express Transit Card" mode in your settings beforehand.

Android: Basically not working

Because the HCE architecture relies on the phone's central operating system, Google Wallet will not work when the phone is powered off. A few devices using hardware security elements (such as Samsung Pay on some Samsung phones) may offer limited support, but this is not the case, and Google does not officially promise this feature.

Explanation of physical principles

Traditional plastic bank cards are entirely passive—the reader's magnetic field powers the chip, so it's "always online." In contrast, a phone's NFC chip requires an active response, which generates power. Apple's solution is to integrate a separate low-power circuit into the secure element, specifically designed for transportation scenarios—because being unable to enter a subway station is a real "emergency," while not being able to buy coffee is a minor inconvenience.

So if you're an iPhone user and frequently take the subway, remember to enable the Express Transit feature. It might save your life on a morning when your battery dies.

Market Structure: Duopoly and Regional Differences

In developed markets, competition in digital wallets has settled mainly into a duopoly between Apple and Google. However, these two giants are not on equal footing.

As of 2025, Apple Pay had approximately 64 million users in the United States, accounting for 49% of the mobile wallet market. Google Wallet, on the other hand, had approximately 35 million users, with a 30% market share. On the surface, the difference doesn't seem significant. However, what's truly astonishing is the difference in transaction activity: as of 2020, Apple Pay accounted for 92% of mobile debit wallet transactions in the United States.

What does this mean? While Google Wallet does have users, their usage frequency is far lower than that of Apple Pay users. iPhone users consider Apple Pay their native payment tool and rely on it extensively in their daily lives. Android users, on the other hand, have multiple payment options (Google Pay, Alipay, WeChat Pay, Samsung Pay, etc.), leading to fragmented usage.

The generational gap is even more pronounced. 73% of Gen Z digital wallet users use Apple Pay weekly. In contrast, less than 15% of Baby Boomers use digital wallets weekly—they prefer physical cards. This generational gap means that as Gen Z's purchasing power grows, the shift to "purely digital" payment experiences will accelerate.

The Chinese Market: The Battle Between QR Codes and NFC

China's payment landscape is an interesting "exception." However, NFC technology accounts for 68% of the global contactless payment market share; QR code payments still dominate in China.

Why? This isn't a technological choice, but rather a result of historical circumstances. When Alipay and WeChat Pay experienced explosive growth between 2013 and 2014, most Chinese merchants lacked NFC terminals, and most consumers' phones didn't support NFC. QR codes offered a "zero-barrier" solution: merchants needed only to print a QR code image, and consumers only required a phone capable of taking photos.

Once established, this first-mover advantage is difficult to shake. Although UnionPay's QuickPass (based on NFC) offers stronger security and faster speeds, its market share remains limited amid the deeply entrenched Alipay/WeChat Pay ecosystem.

However, the advancement of the digital yuan may change this landscape. The digital yuan supports offline payments—transactions can be completed even in situations with extremely weak network signals—which is precisely the inherent advantage of NFC. With the expansion of the central bank's digital currency pilot program, NFC's application in China may experience a second spring.

This case illustrates that the adoption of payment technology depends not only on the quality of the technology itself, but also on the existing ecosystem, user habits, and historical opportunities. Sometimes, "good enough" is more important than "better."

Merchant Perspective: Costs, Challenges, and Opportunities

For consumers, "tap" is convenient. For merchants, it's a complex cost-benefit calculation.

A common misconception is that "Apple Pay is more expensive for merchants." In reality, neither Apple nor Google charges merchants directly. Their revenue comes from a share of the card issuer's exchange fees. Merchants still pay the standard card processing fee.

So why do merchants find Apple Pay expensive? The reason lies in the card type. Users tend to link high-reward credit cards to their digital wallets. These cards themselves have significantly higher exchange fees than regular debit cards (US credit card exchange fees are 1.5%-2.5%, while debit card exchange fees are only 0.05% + $0.21). Therefore, the cost is borne by the card itself, not by NFC technology.

For small businesses, the real obstacle is the cost of hardware. For example, based on publicly available pricing in the US in 2025, a traditional Verifone or Ingenico terminal costs $250-$500. A complete POS system (such as Clover Station) could cost $1,000-$3,000. This is a significant expense for a small street-side shop.

SoftPOS: A Disruptive Solution

The most disruptive trend in 2025 will be SoftPOS (Software Point of Sale). This technology allows merchants to download an app on a regular consumer smartphone and use the phone's NFC chip to receive payments directly.

What does this mean? Hardware capital expenditure drops to zero. A food delivery rider, a pop-up shop owner, a small vendor in an emerging market—all you need is an NFC-enabled phone to accept bank card payments. The global SoftPOS market was already worth over $420 million in 2025 and is projected to grow to $2.93 billion by 2035.

Of course, the security of SoftPOS is a concern. It relies on software authentication and "white-box encryption" to protect the PIN code entered on the consumer-grade mobile phone screen. The PCI MPoC standard has set strict authentication requirements for this. However, compared with professional terminals, SoftPOS still faces a higher risk of application-level malware.

Bottlenecks of legacy systems

While front-end "tap-to-pay" transactions are lightning-fast, many large retailers' backend systems lag. Many systems are designed for end-of-day bulk settlements and struggle to meet modern demands such as real-time membership points and instant fraud detection. Upgrading these systems requires deep integration with the payment kernel—a high-risk, high-cost undertaking for retailers using 15-year-old software. The result is a fragmented user experience: payments can be completed with a tap, but membership cards may still require barcode scanning.

Future Outlook: From Payments to Invisible Interactions

Looking ahead to 2026 and beyond, the act of "paying" itself may become increasingly "invisible".

Biometric payment cards are emerging. These cards embed fingerprint sensors directly and are self-powered by the magnetic field energy of the card reader. Fingerprint verification is completed on the card, and once successful, the card sends a "verified" signal to the terminal, allowing large transactions without a PIN code. This means that contactless payments are no longer subject to spending limits (the UK will remove the £100 cap on March 19, 2026). Market forecasts predict that this sector will grow from $290 million in 2024 to $5.7 billion in 2030, representing an average annual growth rate of 64%.

AI-powered proxy payments represent an even more imaginative direction. Imagine this: your personal AI assistant negotiates purchases on your behalf (such as booking the cheapest flight or ordering coffee), then automatically executes the payment using tokenized credentials. You don't even need to "touch" anything—the AI does everything for you.

But this also raises new trust issues: How to distinguish between user-initiated payments and payments initiated by AI agents? How to ensure that AI operates within predefined spending limits? How should regulators respond when non-fintech companies (Apple, Google) provide financial services through AI agents? These questions are becoming new challenges for policymakers.

Value-added services (VAS) redefine the point of sale from a simple transaction checkpoint into a data-rich interactive node. Apple VAS and Google Smart Tap protocols allow a single tap to complete payment, loyalty points, and receipts simultaneously. Merchants can push personalized offers in real time at the moment of payment, building highly accurate user profiles. Of course, this also raises privacy concerns—every tap leaves a data trail.

Conclusion: The eternal tension between convenience and security

From magnetic stripe cards to chip cards, and from chip cards to "tap to pay," the evolution of payment technology has always been moving in one direction: faster, more convenient, and more frictionless.

But convenience never comes free. New security challenges accompany every technological advancement. NFC's 4-centimeter operating distance is a barrier, but relay attacks attempt to bypass it. Secure Elements offer bank-grade protection but limit openness. HCE brings flexibility but expands the attack surface.

This tension will never disappear. It drives the evolution of technology—from distance-limiting protocols to AI-driven fraud detection, from biometric cards to quantum-secure encryption (addressing the threat posed by future quantum computers to existing encryption systems).

As consumers, all we can do is understand the principles and limitations of these technologies. The next time you tap your phone on the checkout counter, you'll know that behind that "ding" sound lies a sophisticated collaboration of electromagnetic physics, cryptographic mathematics, financial protocols, and security architecture—and a never-ending game of offense and defense.

And this is the story of modern payments.

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Sea Lament: The Rise, Fall and Destiny of the Ryukyu Islands (Part I)

 

The picturesque Ryukyu Islands, where every corner carries a story buried deep in the vicissitudes of history. Along the tranquil azure coastline, beaches are gently caressed by the sea breeze, as if resonating with times from centuries ago. Yet behind this beautiful scenery lies a painful history once forgotten.

In the mid-to-late sixth century AD, Emperor Yang of the Sui Dynasty ordered the cavalry officer Zhu Kuan to set sail and explore distant foreign lands. Zhu Kuan arrived at what is now the northern part of Amami Ōshima and Yonaguni Island. He saw a cluster of islands winding through the waves like pearls, resembling a curled dragon floating on the water. Thus, he gave this mysterious place a name—Liuqiu (流虬, meaning "Flowing Dragon").

Due to language barriers, he captured a local inhabitant and brought him back to the Central Plains. The following year, in the fourth year of the Daye era of Sui, Emperor Yang again dispatched Zhu Kuan to Ryukyu, attempting to pacify the situation. At that time, Ryukyuans often came to the military camps as merchants to trade, indicating that civilian exchanges between China and Ryukyu existed even before they were recorded in official Chinese historical texts, though the exact timing can no longer be verified.

However, the Ryukyuans were unwilling to accept pacification. Emperor Yang of Sui then ordered General Chen Leng of the Martial Guard and Court Counselor Zhang Zhenzhou to lead an army to subjugate Ryukyu. In the army was a Kunlun native who could speak the Ryukyuan language fluently; he was sent to conduct pacification work, but the Ryukyuans still refused to compromise. The Sui army finally launched a military campaign, captured Shuri Castle, burned the city, and took over a thousand men and women captive back to the Central Plains.

Later, when the Tang Dynasty compiled the Book of Sui, considering that "qiu" (虬) means "little dragon" in Chinese and to avoid conflict with imperial titles, the place was renamed "Liuqiu" (流求). It was not until the fifth year of the Hongwu era of the Ming Dynasty (1372) that this place was officially named "Ryukyu" (琉球), implying that it was as precious as glazed jade and pearls. This name has been used ever since. Thus, the history of Ryukyu gradually unfolded its remarkable chapters through exploration, adventure, exchange, and conquest.

During the Qiandao era of the Southern Song Dynasty, "Chinzei Hachirō" Minamoto no Tametomo drifted to Ryukyu, which had not yet established formal relations with China, and fathered a son. This son was named Shunten, who at age fifteen became the Lord of Urasoe. In 1186, during the Chunxi era of Song, the 25th king of the Tenson Dynasty, which originally ruled Ryukyu, was assassinated by the powerful minister Riyu, throwing the Ryukyu Kingdom into chaos. Shunten sent troops to suppress the rebellion and eliminated Riyu. As the last king of the Tenson Dynasty had no heir, the 22-year-old Shunten was enthroned by the ministers the following year. After the fall of the Song Dynasty, Emperor Shizu of Yuan changed "Liuqiu" to "Ruiqiu" and sent troops to conquer, capturing over 130 people before returning. This was the second and final military expedition against Ryukyu by a Central Plains dynasty. Although the Sui and Yuan dynasties had both conducted military campaigns against Ryukyu, neither aimed to annex it. The goal of the Central Plains dynasties was merely to incorporate Ryukyu into China's tributary system, which was finally achieved during the Ming Dynasty.

By the end of the Yuan Dynasty, Ryukyu had divided into three kingdoms: Sannan, Chūzan, and Sanhoku. Among them, the Kingdom of Chūzan was the most powerful. In 1372, the Hongwu Emperor issued summons to all three, and Chūzan's envoy was the first to present tribute at court. After the tributary relationship between Ryukyu and China was established, in the eighth year of Hongwu, Emperor Taizu ordered sacrifices to Ryukyu's mountains and rivers to be conducted in Fujian. When the kings of Sannan and Sanhoku learned of Chūzan's tribute, they also paid tribute to the Ming Dynasty in 1380 and 1383 respectively, officially becoming vassal states of Ming and competing for Ming's recognition and support. As all three kingdoms claimed legitimacy before the Ming Dynasty, conflicts among them were incessant. In the sixteenth year of Hongwu, Emperor Taizu sent the envoy Liang Min and Lu Qian to announce to all three kingdoms, ordering them to cease hostilities. After receiving the imperial edict, the three kingdoms temporarily laid down their arms. In 1429, King Shō Hashi of Chūzan defeated King Tarumai of Sannan, unified the three mountains, established the Ryukyu Kingdom, and made Shuri Castle the capital. The King of Chūzan was enfeoffed by the Ming government as the King of Ryukyu.

In the fifth year of the Xuande era of Ming (1430), Emperor Xuanzong decided to bestow upon the Ryukyuan king the special surname "Shō" (尚). This bestowal carried profound significance, as in ancient China, "shang" (尚) represented the important duty of managing imperial affairs. Emperor Xuanzong's bestowal was clearly well-considered.

From then on, throughout the Ming and Qing dynasties, successive Ryukyuan kings had to receive investiture from China to legitimately ascend the throne. Otherwise, they could only be called "Crown Prince" (世子), temporarily managing state affairs. From Satto to the last king Shō Tai, this investiture system was never interrupted. The political legitimacy of Ryukyuan kings had to be recognized by the Central Plains dynasty; even usurpers like Kanamaru had to pretend to be the legitimate king's son, change his name to "Shō En," and request imperial investiture. In 1472, Emperor Xianzong of Ming invested Shō En as King of Ryukyu Chūzan, opening the curtain on Ryukyu's Second Shō Dynasty.

However, the relationship between China and Ryukyu was not limited to political investiture. From the twenty-fifth year of Hongwu (1392), Emperor Taizu of Ming allowed children of Ryukyuan royalty and high officials to study at the Imperial Academy. Meanwhile, given the navigational difficulties faced by Ryukyuan envoys traveling to China, China specially granted thirty-six families from Fujian to settle in Ryukyu; they were experts in shipbuilding and navigation. These Fujianese were not only skilled in navigation but also served as interpreters and handled other important tributary affairs. This measure aimed to promote the values of the suzerain through Chinese immigrants to Ryukyu, spreading Confucian thought and Chinese culture, attempting to let Chinese cultural ideas represented by Confucianism take root in the vassal state.

Among the thirty-six families sent to Kume in Ryukyu, those from Fuzhou were primarily surnamed Zheng, Yang, Lin, Liang, Cheng, and Jin; those from Quanzhou were mainly surnamed Cai; and those from Zhangzhou were primarily surnamed Ruan and Mao. From the early Ming bestowal of the thirty-six families during Hongwu to the mid-Ming Wanli era, over two hundred years, the influence of the thirty-six families in Ryukyu did not grow stronger but gradually waned. By the end of the Wanli era, most of the Kume thirty-six families had either died out or changed their surnames, with few remaining. It had become virtually impossible to rely entirely on the descendants of these early Ming Kume thirty-six families to serve as chief historians and interpreters. In the thirty-fifth year of Wanli (1607), King Shō Nei petitioned the court "to follow the precedent of the Hongwu-Yongle eras and again bestow thirty-six families to enter Ryukyu to continue serving in their duties." The request was politely declined by the Ministry of Rites. Unable to obtain another opportunity for Chinese households to be sent to Ryukyu, the Kume thirty-six families thereafter received no fresh blood from mainland China.

The fall of the Ming regime and the end of Ming-Ryukyu tributary relations once plunged Ryukyu into confusion, while also providing multiple possibilities for handling its foreign relations. Ultimately, Ryukyu established a suzerain-vassal tributary relationship with the Qing Dynasty, becoming a member of the East Asian tributary system centered on Qing. The establishment of Qing-Ryukyu tributary relations accompanied the mutual struggles and games among various power groups during the Ming-Qing transition. In this process, Ryukyu chose the Qing Dynasty—the most powerful entity capable of providing Ryukyu with national security guarantees and economic benefits—maintaining its national polity and economic-social development within the framework of the tributary system led by Qing. The internal motivations for this choice were primarily based on considerations of realism, along with the historical accumulation of centuries of Sino-Ryukyuan tributary relations and the value identity it conferred, the realistic interests of the maritime merchant groups that dominated Ryukyu's economic and trade activities, and Ryukyu's national character of serving the great power and self-deprecation. The establishment of Qing-Ryukyu tributary relations allowed Ryukyu to return to its previous position at a historical juncture when the Ming-Qing transition and the East Asian maritime power configuration were complex and volatile, securing a stable political and economic environment to maintain its overseas trade development and ensure its continued existence as "an independent nation" until its demise 230 years later.

For over four hundred years, from the second year of Yongle in Ming (1404) to the fifth year of Tongzhi in Qing (1866), Ryukyu was profoundly influenced by Chinese culture, with Chinese as its official language. After the thirty-six Fujianese families arrived in Ryukyu, they received great respect from the royal court down to the common people. The Ryukyuan king not only "bestowed surnames upon his ministers," adopting Chinese names, but later expanded this practice from the nobility to commoners, while ordering all major clans to compile genealogies. From then on, every Ryukyuan family could clearly trace its lineage, rank, and seniority like Chinese clans, helping Ryukyuans revere their ancestors and trace their roots, gradually guiding Ryukyu to develop into a "Land of Propriety." The "thirty-six Fujianese families" in Ryukyu were mainly responsible for navigation, shipbuilding, drafting diplomatic documents, translation, and trade with China. Their descendants maintained a dominant position in Ryukyu with their Mandarin ability and Confucian learning, mostly entrusted with important responsibilities, participating in major national political, economic, and cultural activities, and enjoying high official positions for generations—some even rising to the position of Prime Minister, such as the famous Prime Minister Sai On. Kume Village, whose name means "eternally enjoying salary," became the center for transmitting Chinese culture and advanced production techniques to Ryukyu.

As China's only port trading with Ryukyu, Fujian bore an important mission in Sino-Ryukyuan exchanges. Many Chinese folk customs brought by the thirty-six Fujianese families, such as the Qingming Festival, turtle-shell tombs, and "Taishan Shigandang" stone tablets, though tempered over centuries, still bear striking similarities to those in China's Fujian region today. It can be said that Ryukyuans first came into contact with Fujian, and through it came to know China.

Since the thirty-six Fujianese families arrived in Ryukyu in early Ming, the Fujianese have always observed ancestral worship during Qingming. To this day, tens of thousands of Ryukyuans collectively visit graves on the two Sundays around April 5th each year, with celebrations no less grand than in China. Besides Qingming, Ryukyuan customs such as the Dragon Boat races on May 5th, the Rice Festival in June, and ancestral worship during the Mid-Autumn Festival on July 15th are all similar to customs in Guangdong, Guangxi, and Fujian.

Ryukyuan tombs are built with stone on three sides, "shaped like a half-moon, raised at the back and sloping forward," resembling a turtle shell, hence called "turtle-shell tombs." This style of tomb can be seen everywhere in southern Fujian, China, and is one of the typical items indicating the close connection between Ryukyu and southern China. "Taishan Shigandang" was once a widespread folk spirit-stone worship phenomenon in China. In rural northern Fujian, people believed Mount Tai to be the source of righteous energy in the world, while crossroads and three-way intersections were prone to evil spirits. Therefore, people customarily erected stone tablets inscribed with "Shigandang" or "Taishan Shigandang" at house entrances facing such locations to suppress evil spirits. Japan's Shigandang belief originated in the Tang Dynasty and was introduced to Ryukyu in the 14th-15th centuries, then spread from the main island to the villages below. On Ryukyuan streets, especially at T-intersections, one can often see stone tablets inscribed with "Shigandang" or "Taishan Shigandang" used to ward off evil. In the mid-Ming period, Chinese feng shui was introduced to Ryukyu, and Shigandang is a clear example of its influence. With changes in architectural styles, Shigandang has become rare in China, but it has been well preserved in Ryukyu. To this day, when Ryukyuans build new houses or roads, if they encounter a T-intersection, they still erect Shigandang to ward off evil spirits.

The Ming and Qing periods were the golden age of Chinese architectural culture. Deeply influenced by Ming-Qing architectural culture, especially that of southern China, Ryukyu's garden architecture such as Shuri Castle, Fukushū-en Garden, and stone lions all retain a strong Chinese architectural legacy, especially that of Fujian. Shuri Castle, located east of Naha, the capital of Okinawa Prefecture, was once the capital of the Ryukyu Kingdom. "The walls of Shuri Castle not only adopted the Fujian traditional architectural technique of 'brick-and-stone layering,' but even some of the stone materials were directly transported from Fujian." On the slope leading to Shuri Castle, the Shureimon Gate with its plaque reading "Land of Propriety" is particularly eye-catching. Inside Shuri Castle, plaques such as "Eternal Land of Chūzan" are displayed, and the pillars in front of the main hall are carved with four-clawed dragon images. This is evidence of the Ryukyu Kingdom's status as a Chinese vassal state, as only imperial Chinese garden architecture could feature five-clawed dragon carvings. Even more interestingly, the main hall of Shuri Castle does not face south but west, mainly because China, Ryukyu's suzerain, was located to Ryukyu's west. All of this reflects the Ryukyu Kingdom's submission to China and its admiration for Chinese culture.

Throughout Ryukyuan history, the island where Fujianese Chinese lived was called "Tang Camp" (唐營), and the martial arts they brought from China were called "Tang Hand" (唐手). Tang Hand spread from Ryukyu to mainland Japan, directly giving birth to Japanese "Karate." Many Kume residents, in addition to Japanese names, particularly those with strong Chinese sentiments, still give their children Chinese names despite government opposition, to remember their Chinese ancestors. Kume Village remains the most concentrated settlement of Chinese culture in Ryukyu today, hosting annual Confucius worship ceremonies.

Over centuries of development, although Ryukyuan culture has undergone many changes, it has preserved numerous elements of Chinese culture, especially southern Chinese culture, in customs, architecture, language, and many other aspects. These preserved cultural elements are the best historical witnesses to Sino-Ryukyuan cultural exchange.

The Ryukyu Kingdom was always an independent trading nation, and its geographic location made it a trade hub between China, Japan, and Southeast Asia. The force that transformed Ryukyu into a trading kingdom came from China, not Japan. During the Ming and Qing periods, Sino-Ryukyuan trade activities included, in form, tributary trade and private trade, with tributary trade further divided into investiture trade and tribute trade. In nature, it was divided into official trade and private trade. Private trade was further divided into legal and illegal types. Any private trade conducted within government-permitted scope during investiture or tribute missions was legal; all other private trade was illegal. Trade between the Ming government and Ryukyu was typical official tributary trade. Official tributary trade, which developed in China from the Han Dynasty, was based on an ideology of Chinese economic superiority, requiring countries surrounding China to pay homage to the emperor, in return for which they received generous gifts. Tributary states were granted the privilege of trading at certain ports. Some goods were transported to individual countries in East and Southeast Asia, sold or distributed to political allies. At the official level of interstate interaction, tributary trade was the official commercial means.

In tributary trade, all mission members received generous gifts of gold, silver, porcelain, and silk. Besides the mission members who went to the capital for tribute, large numbers of Ryukyuan attendants stayed at the "Ryukyu Hall" in Fujian. Since Sino-Ryukyuan trade was mainly for the Ming government to politically "cherish distant peoples" and establish suzerain status rather than to seek economic profit, the Ming government purchased at high prices the "tribute goods" (actually Ryukyuan merchandise) brought by these people. Official tribute items were traditionally not priced. This trade had a strong political character and also created great economic pressure on the Ming government.

Ming Dynasty maritime policy was generally conservative, though it varied in strictness. From 1371 to 1394, the Ming government issued the "not a single plank may enter the sea" prohibition four consecutive times. This marked the beginning of the Ming government's "maritime prohibition system," but while implementing the maritime ban, Ming allowed and encouraged tributary trade from vassal states. The Ming government hoped to monopolize foreign trade through tributary trade that combined investiture with commerce, thus gaining government revenue and vassal tribute submissions while achieving the goals of suppressing merchants and controlling the people to maintain order—truly killing two birds with one stone.

The maritime prohibition policy did not allow private maritime trade, and the Ming government had strict regulations on tribute periods for vassal states; obtaining needed goods through tribute alone was quite limited. Under these conditions, the Ryukyu Kingdom saw the business opportunity for trade with Southeast Asian countries. It then petitioned the Ming government, citing its small size and weakness and lack of ships for tribute. With China's help in granting people, ships, and favorable tribute terms, Ryukyu quickly built trade bridges with Southeast Asian countries and eventually became the "Bridge of Nations."

Ryukyu was always able to exchange "tribute horses and local products" for generous rewards, and its surplus goods beyond tribute were allowed to be sold at the guesthouses. After completing tribute in the capital, Ryukyuan envoys would go to Fuzhou to return by ship. The returning ships carried both imperial gifts and large quantities of porcelain and silk secretly purchased by mission members in Fujian and Zhejiang. The silver from selling their own goods and the Chinese merchandise they carried became Ryukyu's foundation for trading with Southeast Asian countries to the south.

Ryukyu's trade with Southeast Asia had many prerequisites, mainly depending on the state of Ming government maritime policy. Ryukyu seized the opportunity of tributary trade precisely when the maritime ban was strictly enforced, Chinese merchants had declined, and vassal states wanted Chinese goods but were not permitted frequent tribute. It quickly began and gradually expanded trade with Southeast Asian countries, launching its own "Age of Great Navigation" in 1425.

The basic route of Ryukyu's trade with Southeast Asia was: departing from Naha Port on the northeast monsoon in August-September each year, traveling along the Fujian and Guangdong coasts to Annan (today's Vietnam) and Siam (today's Thailand), then branching into two routes. One continued westward along southern Siam, sailing southwest via Patani (today's southern Thailand) to Malacca, quickly completing trade business, then riding the southwest monsoon in March-April of the following year to travel north via Sumatra, Palembang (today's Indonesian port), Java, then returning to Ryukyu via Sulu and Luzon. The other route went directly south to Java, completed trade business, then returned to Ryukyu northward along the Luzon-Sulu line. These two routes together constituted the "Ryukyu Network" of that era.

Through over a century and a half of trade with Southeast Asia, Ryukyu gradually deepened its understanding of Southeast Asian countries' customs and conditions through maritime practice. This was reflected in Ryukyu's "one ship, two uses" approach of sending missions to two countries simultaneously: to Annan primarily with royal decorative items plus 20,000 jin of pig iron; to Siam primarily with daily utensils like folding fans and porcelain. Ryukyuans always observed the local laws and customs of trading countries. Even when Ryukyuans caused "fighting incidents" during trade with Malacca in the Chenghua era, the Ryukyuan king quickly dealt with the relevant personnel after the ship returned, formally apologized in diplomatic correspondence, and proposed: "If our envoys commit improprieties in the future, please inform us for punishment, so that neither side is disappointed and our alliance may last forever." This self-disciplined principle of keeping one's place was also an important reason for Ryukyu's continued relations with Southeast Asian countries.

As Ryukyu expanded its interactions with Southeast Asian countries, it gradually formed a fixed route: Ryukyu Islands—Malay Peninsula—Strait of Malacca—Sumatra—Java—Philippine Islands—Ryukyu Islands. This was both the result of Ryukyu's century and a half of trade practice and the driving force for its continued maritime trade development. However, this transit or intermediary trade was an abnormal trade form under specific conditions, an unsustainable trade method built on the unequal exchange of tributary trade between Ming and Ryukyu. The prerequisite for Ryukyu's trade with Southeast Asian countries was obtaining large quantities of Chinese goods popular in those regions, and this prerequisite was greatly affected by Ming government maritime policy. The later decline of Ryukyu's transit trade confirmed this: once the maritime ban was lifted, Chinese merchants' influence in Southeast Asia would resurge, and Ryukyu could not compete equally with Chinese merchants in either commodity prices or supply channels. Additionally, Portugal's occupation of Malacca in 1511 would also create enormous pressure on Ryukyuan merchant ships heading south. Therefore, the Ryukyu trade network was an unstable product of a specific period.

The exchange between Ryukyu and Southeast Asia brought great influence to both regions, especially Ryukyu, and Ryukyu's reputation as the "Bridge of Nations" came from this. Unfortunately, Ryukyu did not see the crisis within its prosperous trade. Under the dual competitive pressure from Westerners and Chinese merchants, Ryukyu's previous practice of gaining large profits through transit alone was obviously no longer viable. At this time, Ryukyu did not invest transit trade profits into learning and improving product crafts—such as introducing Chinese porcelain technology to manufacture porcelain products with Ryukyuan characteristics, or learning lacquerware crafts from neighboring Japan. Commercial wealth, entirely controlled by the royal family, was used for building temples and palaces and importing Buddhist scriptures, without deep understanding of its dependence on and vulnerability of transit trade. Thus, with depleted financial resources, national strength gradually declined, becoming an important cause for Ryukyu's troubled fate thereafter.

On June 8, 1582, Kamei Korenori (1557-1612), lord of Shikano Castle in Inaba Province (today's eastern Tottori Prefecture), seeing that his master Toyotomi Hideyoshi was about to unify Japan, requested that his master grant him Ryukyu. Toyotomi Hideyoshi was noncommittal. This shows that Japanese had already coveted Ryukyu at that time. In 1587, the Shimazu clan of Satsuma Domain suffered Toyotomi Hideyoshi's subjugation campaign, facing a regime crisis, and was forced to submit under great pressure. Under these circumstances, preventing Kamei from assuming the position of "Governor of Ryukyu" became the Shimazu regime's urgent priority. In 1589, an envoy of King Shō Nei of Ryukyu came to Tōan at Tenryū-ji Temple in Japan to meet Toyotomi Hideyoshi, outwardly making a gesture of Ryukyuan submission to the Toyotomi clan. In 1592, Toyotomi Hideyoshi issued vermilion seal letters to Shimazu Yoshihiro and Shimazu Yoshihisa, deciding to make Ryukyu a "yoriki" (auxiliary warriors) of the Shimazu clan. This "yoriki" appointment became the so-called basis for Shimazu Yoshihisa's demand in February 1604 that King Shō Nei acknowledge Ryukyu as Satsuma's "vassal."

In the winter of 1602, a Ryukyuan ship drifted to Mutsu Province (today's Aomori, Iwate, Miyagi, Fukushima prefectures and part of Akita). The following spring, Tokugawa Ieyasu ordered his subordinates to return the ship's crew to Ryukyu, but used this as a reason to demand that Ryukyu send a mission of thanks to Japan. This was considered an offense to the Ming central government, as the intent was extremely obvious: "To instigate Ryukyu to help Japan negotiate peace with the Ming government, Ryukyu must first be made to submit to Japan."

In 1609, with permission from the Tokugawa shogunate, Shimazu Iehisa brazenly invaded Ryukyu. A descendant of the Zheng family, one of the "thirty-six Fujianese families," led his entire clan in resistance but was defeated and captured. The Japanese cruelly executed the Zheng patriarch by boiling in oil; as he died, he pulled two Japanese guards into the oil cauldron with him. This event spread throughout Ryukyu, and Ryukyu changed its national emblem because of it. Today, "the center of Ryukyu's national emblem is a red circle with three black C's inside, symbolizing the scene of three people being boiled to death in an oil cauldron," also expressing Ryukyuans' commemoration of the Zheng family. Shuri Castle, the Ryukyuan capital, fell. Satsuma's invasion of Ryukyu changed the equal status between Japan and Ryukyu from then on; this invasion placed Ryukyu under Japanese rule. Japanese troops pillaged and burned the occupied Ryukyu Kingdom, and the wealth Ryukyu had accumulated through foreign trade over the years was completely looted. Since China was enforcing a maritime ban against Japan at this time, normal trade between China and Japan was impossible. To obtain greater trade profits, Japan decided to use Ryukyu's special relationship with China for trade, and thus the originally independent Ryukyu-China trade was secretly controlled by Japan.

In 1610, Shimazu Iehisa coerced Shō Nei to pay homage to the Edo shogunate. The second shogun, Tokugawa Hidetada, ordered Shō Nei to "grant Ryukyu's tribute taxes to Iehisa." The reason for not abolishing the King of Chūzan was that the Tokugawa regime wanted to use Ryukyu to conduct peace negotiations with Ming. To smoothly complete peace negotiations, Japan at that time had to acknowledge the suzerain-vassal relationship between Ryukyu and the Ming government. But while outwardly showing goodwill to Ming, Satsuma, under shogunate direction, also issued ruling decrees represented by the "Fifteen Articles," attempting to incorporate Ryukyu into the bakuhan system.

In 1634, the third Tokugawa shogun Iemitsu issued a fief and stipend edict to the Shimazu clan, generously rewarding them and intending to "Japanize" the Ryukyu issue. Satsuma changed the Shō clan's title from "King of Chūzan" to "Ryukyu Kokushi" (Governor of Ryukyu). The title "Ryukyu Kokushi" first appeared in a letter written by Shimazu Iehisa to the Spanish colonial governor of Luzon in 1615. At that time, Japan fabricated the nonexistent title "Ryukyu Kokushi" to "conveniently explain to the Spanish side Ryukyu's international status as a vassal state of Satsuma." Cunning Japanese politicians wanted to use the strategy of ambiguous "translation" to achieve their political goal of annexing Ryukyu; this title also intended to incorporate Ryukyu into the "King—Lord—Governor" bakuhan system structure.

With the Ming-Qing regime transition, the positioning of Japan-Ryukyu relations also quietly changed. In 1633, when Ryukyu received Ming investiture envoys, Satsuma boldly speculated that "the Ming government must have tacitly acknowledged Japan's control over Ryukyu, so we can consider presenting some gifts to the Ming investiture envoys (as thanks)." But by 1683, when Qing investiture envoys crossed to Ryukyu, "Satsuma officials claimed to be from Treasure Island (Ryukyu), hiding their Japanese identity when dealing with the investiture envoys." This was because the Japanese feared friction with Qing over control of Ryukyu and adopted the tactic of concealing their identity. The "Regulations for Travelers" policy formulated by the Ryukyu royal government in 1753 also mentioned that if Japanese were seen by Qing nationals within Ryukyu, Japanese were allowed to claim to be Ryukyuans from Treasure Island. Even until the end of the Tokugawa era, Japanese could often be seen using this tactic. However, in 1848, when Western ships frequently visited Japan, the Japanese "Guidelines for Answering Foreigners" showed a different response pattern: "When Yamato ships are questioned by other ships (Western ships), they should answer that they are Japanese Treasure Island ships." This shows that during the transition from early modern to modern times, on issues involving Ryukyu, Japan adopted asymmetric approaches when dealing with China and the West—first to let the Qing central government lower its guard; second to prove to the West that Japan possessed sovereignty over Ryukyu.

In 1853, Commodore Matthew Perry of the U.S. Pacific Fleet led four "Black Ships" to forcibly open Japan's doors, causing enormous shock to Japan under Tokugawa rule. To guard against Perry making an issue of Ryukyu, Senior Councilor Abe Masahiro compiled a Q&A collection titled "General Ideas for Handling the Ryukyu Issue." From this time, the Japanese began worrying that Western powers might intervene in Ryukyu's Sino-Japanese "dual affiliation" status.

In 1854, Perry signed the Treaty of Kanagawa with Japan at Uraga Port on mainland Japan, and the Treaty of Amity with Ryukyu in Naha, Okinawa. In form and content, the former "used Japanese-English bilingual text with Western calendar and Japanese era names," was "a treaty between nations (The Treaty of Peace and Amity)," and was "bilateral obligation" type; the latter "used Chinese-English bilingual text with Western calendar and Qing era names," "was not an equal 'agreement' or 'compact' (Articles of Agreement)," and was "unilateral obligation" type. On this issue, rather than saying Ryukyu belonged to Japan, it would be more accurate to say Ryukyu should originally have been China's vassal state. Subsequent actions by some great powers confirmed this—France in 1855 and the Netherlands in 1859 both used "Chinese-English bilingual text with Western calendar and Qing era names" to sign treaties with Ryukyu.

At this time, the Qing Empire, severely damaged in two Opium Wars, had lost initiative in politics, economy, military, diplomacy, and security, and with frequent internal rebellions had no time to attend to border affairs, giving Japan an opportunity. In 1871, Japan implemented the abolition of domains and establishment of prefectures nationwide, treating Ryukyu as a ryōseikoku (administrative district) under Kagoshima Prefecture's management. In November of that year, ships from Miyako Island and other outer Ryukyuan islands heading to Shuri royal court to submit annual tribute encountered a typhoon on their return voyage. One ship drifted to Bayao Bay (today's Manzhou Township, Pingtung County) at Taiwan's southern tip; the crew who went ashore were attacked by Taiwan aborigines, 54 were killed, and another 12 escaped and were sent by Han Chinese residents to Fengshan County, then by the county magistrate to Fuzhou's Rouyan Station for settlement. In May 1873, Japanese Foreign Minister Soejima Taneomi came to China to bring up this old matter, protesting to the Qing government over the "Bayao Bay Incident" and demanding compensation. The Qing government, having already given relief to the Ryukyuans, refused compensation. Under questioning by the Japanese envoy, Zongli Yamen Minister Mao Changxi surprisingly said: "The killers were all raw savages, temporarily placed beyond civilization, and inconvenient to prosecute thoroughly." Japan seized on this: since the Qing government acknowledged that Taiwan's eastern aborigines were "raw savages," they were not subjects under Qing jurisdiction; since it was "inconvenient to prosecute thoroughly," it was not a place governed by Qing. Therefore, Japan sending troops to punish "raw savages" would not constitute aggression against China. This provided a pretext for Japan's later invasion of Taiwan.

In May 1872, Meiji government elder Inoue Kaoru submitted a memorial titled "On the Disposition of Ryukyu" to the government, recommending further clarification of Ryukyu's status. Thereafter, Inoue coerced the Ryukyuan king to Tokyo and demanded that Ryukyu quickly align with Japanese mainland systems regarding administrative divisions and tax contributions. In handling Ryukyu, the Meiji government not only skillfully used "The Law of Nations"—the colonialist rules representing the new international order of that time—but also skillfully utilized the "investiture system" under the concept of "Chinese-barbarian order," choosing the route of "vassalization." It first made Ryukyu appear in a "dual affiliation" state, having King Shō Tai receive investiture from both China and Japan. After controversy arose, it gradually stripped away sovereignty through its own powerful strength. In June of the same year, the Japanese government unilaterally announced the abolition of the Ryukyu Kingdom, renamed it Ryukyu Domain, and enfeoffed Shō Tai as Domain King of Ryukyu. The establishment of "Ryukyu Domain," called by the Japanese the "First Ryukyu Disposition," was both a test by the Japanese government to implement its foreign expansion policy and its first step toward devouring Asia. It was precisely with the success of this first step that Japan's subsequent invasion of Taiwan, military campaign against Korea, and First Sino-Japanese War followed.

The Qing government's "beyond civilization" theory encouraged domestic Japanese calls to "conquer Taiwan." After the "Bayao Bay Incident," Ōyama Tsunayoshi, councillor of Kagoshima Prefecture, proposed the "Theory of Taiwan Subjugation," requesting that the Meiji government send troops to Taiwan to punish the "raw savages." In May 1874, the Japanese government appointed Army Lieutenant General Saigō Tsugumichi as Taiwan Affairs Governor, leading 3,658 troops to Taiwan, applying pressure on the Qing government in the name of "punishing murderers" and testing the Qing government's concern for Taiwan and Ryukyu. Eager to end the conflict, the Qing government, in the Beijing Treaty signed on October 31, acknowledged that "Japan's actions this time were originally undertaken to protect its people as a righteous act, which China does not consider wrong." Meanwhile, China also obtained Japan's promise that regarding Taiwan's raw savages, "China itself will devise ways to properly restrain them." Acknowledging Japan's "righteous act to protect its people" actually acknowledged that Ryukyuans were under Japanese management. To protect Taiwan, the Qing government began acknowledging Ryukyu's "dual affiliation" status, meaning the Qing government no longer firmly maintained the suzerain-vassal relationship but intentionally weakened its suzerainty over Ryukyu.

After the Beijing Treaty was signed, Japan accelerated its annexation of Ryukyu. In May 1875, Japanese troops invaded Ryukyu for colonial rule, preventing Ryukyu from paying tribute to China and blocking congratulations for the Guangxu Emperor's enthronement ceremony. While Japan continuously implemented its occupation plans, the Ryukyu Kingdom repeatedly sent people to China for help. In October 1876, the Ryukyuan king secretly sent Shō Tokuhiro and others to China by ship, beginning a long movement to save the nation. The following year, after Shō Tokuhiro's group arrived in Fuzhou, they submitted King Shō Tai's petition to Fujian-Zhejiang Governor-General He Jing and Fujian Governor Ding Richang, reporting Japan's attempt to annex Ryukyu to the Qing court. He and Ding immediately reported this to the court and recommended that He Ruzhang, about to be sent to Japan, directly negotiate with Japan. However, at this time, Yakub Beg was invading China's Xinjiang in the northwest, and the court had no time to look east to Ryukyu. It merely ordered He Ruzhang to be envoy to Japan, preparing to resolve the issue through diplomatic channels, but sent not a single soldier to Ryukyu. The Qing court issued an edict ordering the Ryukyuan officials who came to petition to return home first.

He Ruzhang was ordered to negotiate with Japan on the Ryukyu issue, arguing vigorously and hoping to preserve Ryukyu's independent status. On May 29, 1878, in a letter to Li Hongzhang, he expressed his views: first, from a geopolitical perspective, Ryukyu was very important to Korea and Taiwan; second, losing Ryukyu would endanger China's future border security. Therefore, he proposed that Ryukyu "must be contested." Li Hongzhang's attitude toward the Ryukyu issue in his reply to He Ruzhang appeared dismissive: "Ryukyuan tribute has no great benefit; if we contend with force over a small country's meager tribute, pursuing empty fame while devoting effort to distant strategy, we not only have no time for it but it would also be meaningless." He viewed the handling of the Ryukyu issue as merely fighting for tribute; in his view, Ryukyu was too far from China, and there was no need to compete with Japan over it.

Regarding responding to the Ryukyu crisis, He Ruzhang proposed three strategies to the Zongli Yamen: the upper strategy was to first send warships to question Ryukyu, demand its tribute, and show Japan that we must contest; the middle strategy was to state our case clearly, ally with Ryukyu and coordinate an attack, showing Japan that we must rescue; the lower strategy was to repeatedly debate, and if not heeded, either cite international law to censure or invite various countries' envoys to judge. Li Hongzhang believed that "sending warships to question and allying with Ryukyuans for certain rescue both seem like making a mountain out of a molehill, appearing alarmist." On one hand, Li Hongzhang was pressured by the "Qingliu faction"; on the other hand, he feared provoking Japan to use force. Therefore, he did not advocate a tough policy toward Japan, did not adopt He Ruzhang's upper and middle strategies, and only emphasized using the lower strategy. He believed the strategy toward Japan was "if words are not heeded, repeat them"—this would serve two purposes: Japan, "knowing its reasoning was inadequate," might not rush to abolish the domain and establish a prefecture, allowing Ryukyu to preserve itself; meanwhile, China would not need to send troops across the ocean. Li Hongzhang's opinion was ultimately adopted by the Zongli Yamen. Without full support from the Qing government, He Ruzhang still conducted negotiations in Japan.

On September 27, 1878, in a Sino-Japanese dialogue between He Ruzhang and Japanese Foreign Minister Terashima Munenori, Terashima stated: "Three hundred years ago we assumed the duty of governing Ryukyu. At that time we appointed Satsuma to oversee Ryukyu for the government. We sent our countrymen to Ryukyu to help them with politics, and correspondingly, Ryukyu also sent officials to our mainland to consult on various governmental operational methods... In any case, whoever levies taxes on a land is its administrator. This fact can be known from international law and other documents... Although historical records show Ryukyu as a vassal state, we should now judge from the perspective of actual governance. Historical records are beyond the reach of actual governance, so historical records are insufficient as evidence." The Meiji government used taxation as its "basis" for claiming sovereignty over Ryukyu under the banner of "The Law of Nations," going so far as to openly declare "historical records are insufficient as evidence." In that same dialogue, the Qing government once proposed inviting Western countries to intervene in this matter. Terashima became angry on the spot: "I say this entirely for your country's sake. For three thousand years, Ryukyu has been our possession, and we have also willingly let Ryukyu be your vassal state. Morally speaking, we have already given your country enough face," and so on. In fact, Terashima's concepts of "possession" and "vassal state" were confusing. A "vassal state" is basically a country with independent sovereignty, but the concept of "possession" is broader, even ambiguous, with possibly different interpretations in different contexts. For example, Terashima's "Ryukyu has always been our possession" could be interpreted as "Ryukyu has always been part of Japanese territory." In the dialogue, Terashima mixed and reversed these two concepts, leaving He Ruzhang, who did not understand colonialist logic and the so-called "Law of Nations," momentarily unsure how to respond, leading him to think that "possession" and "vassal state" were anyway "territory" concepts in "The Law of Nations," leaving no time for detailed consideration. In that special context, the Japanese "translation" strategy indeed played a huge role in promoting colonialist policies; even today, some Japanese legal scholars still use this logic and strategy to "respond" to China's rise.

The Japanese government of that time dominated the negotiating table on the Ryukyu attribution issue with such strategies. Thus, negotiations over Ryukyu attribution became a discourse game in which the Meiji government freely manipulated old and new rule concepts, and this game almost always ended with Japanese schemes succeeding. After several rounds of negotiation, Japan no longer acknowledged Ryukyu's "dual affiliation" but defined "jurisdiction" by whether taxes were levied on a region. Facing China's protest that "the people don't trust you; you cannot be the ruler," Japan retorted: "Just like your Yunnan, even if those natives don't submit to your rule, you have no reason to abandon them." Facing China's statement that "indeed, our dynasty has definite proof of enfeoffing kings and receiving tribute," Japan continued to argue: "For example, Siam once also paid tribute to your country, but Siam has now left you and no longer pays tribute. Moreover, your tribute and our taxation cannot be mentioned in the same breath." As long as Japan kept citing examples of how vague the "vassal state" concept in the Chinese civilization sphere was and how incomplete China's "jurisdiction" was, Japan could always "win" in debates. For another example, facing China's declaration that "Ryukyuan kings must receive investiture from our dynasty to qualify as King of Chūzan," Terashima continued to refute: "Previously, when Western European nobles wanted to become emperors, didn't they all go to Rome to receive investiture from the Pope? This is similar to your investiture. But having the right to invest does not mean you have the right to control, just as Rome could not control other European countries." Terashima completely denied the connection between "enfeoffing kings" and "legitimacy of rule" in the Chinese civilization sphere. However, Japan seemed to have forgotten that it had itself used investiture theory logic for diplomatic affairs in 1872 (Meiji 5); now it wanted to completely deny the theoretical logic of tributary investiture, presenting itself as a "thorough" member of the "Law of Nations Club."

Meanwhile, Li Hongzhang was undermining from behind, writing to the Zongli Yamen, criticizing He Ruzhang's actions as likely to cause Sino-Japanese conflict, believing He "though very brilliant, lacks experience in negotiations, and is somewhat too aggressive." In early 1879, Zuo Zongtang, in a memorial on the Ryukyu issue, believed that Ryukyu was economically poor and its products far inferior to Japan's; politically it dared not offend Japan because, with islands connected to Japan and geographic pressure, it had become a nephew-uncle relationship. The conclusion was that Japan's annexation of Ryukyu was expected, and China could ignore it. His memorial echoed Li Hongzhang's position.

Ryukyu hoped the Qing court would help restore its nation. Although the Qing court ordered Shō Tokuhiro and others to return, they insisted on staying in Fuzhou to wait, inadvertently waiting for three years. After Japan discovered the Qing court's true situation and learned it had no determination to go to war, on March 27, 1879 (Meiji 12), Matsuda Michiyuki, as Ryukyu Disposition Officer, led 160 police officers and a military force of 400 to forcibly seize Ryukyu, abolish Ryukyu Domain, and establish Okinawa Prefecture. At that time, Japanese troops "extensively plundered documents, cultural relics, and official seals exchanged between China and Ryukyu, as well as Ryukyuan government archives, including the original treaties of amity between Ryukyu and the United States and other countries, attempting to destroy and conceal historical evidence, dilute history, and forced King Shō Tai and others to relocate to Japan." This implementation of the domain abolition and prefecture establishment policy toward Ryukyu was also called by the Japanese the "Second Ryukyu Disposition."

The Ryukyu Kingdom urgently requested Qing government aid. The king first sent Mao Fengrai to seek help from He Ruzhang, China's minister to Japan, and also entrusted Fujian merchants going to Japan to carry secret letters to the Fujian governor. Shō Tokuhiro and others, still waiting for news in Fujian, upon hearing that the king had been captured and the country destroyed, deeply felt the crisis of national extinction was imminent and decided to bypass the Fujian-Zhejiang Governor-General and go directly north to petition for military aid. Shō Tokuhiro, along with Cai Dading and Lin Shigong—political activists of the late Second Shō Dynasty—shaved their heads, changed their clothes, disguised themselves as merchants, and rushed to Tianjin to see Li Hongzhang, directly stating Japan's ambitions and earnestly requesting the Qing government to send troops to save Ryukyu from fire and water. Cai Dading and Lin Shigong's group knelt for long periods outside the Donghua Gate, weeping and requesting Qing court aid when court ministers entered. The Zongli Yamen, fearing discussion pressure, reminded Li Hongzhang that abolishing Ryukyu concerned national dignity. In May, Li Hongzhang and others invited former U.S. President Ulysses S. Grant, then touring China, to mediate. Based on Grant's suggestions, Japan proposed the "Island Division and Treaty Revision Theory," designating "Ryukyu's Miyako and Yaeyama Islands near Taiwan as under Chinese jurisdiction to demarcate the two countries' borders." But the condition was revising the Sino-Japanese Treaty of Commerce, with Japan gaining free trade in China's interior and "most favored nation" benefits. The Qing Zongli Yamen proposed "tripartite division of Ryukyu" in negotiations (northern islands to Japan, central islands to restore Ryukyu, southern islands to China), but was rejected by Japan, and Qing's effort to "restore Ryukyu" failed. At this time, the Qing government was negotiating with Russia over the Ili issue, and fearing Japan-Russia collusion, was prepared to agree to Japan's demands. Facing negotiations on both eastern and western fronts, the Qing ruling group had different opinions on negotiating with Japan over Ryukyu. "Some advocated that the old Sino-Japanese treaty should not be changed and the Ryukyu case should not be immediately concluded, such as Right Vice Censor Chen Baochen; some advocated that the old Sino-Japanese treaty could be changed and the Ryukyu case could be concluded as discussed, such as Left Vice Censor Zhang Zhidong." Others "feared Japan might collude with Russia, making things even harder to handle." Opinions varied without consensus. On October 24, 1879, Ryukyuan liaison officer Mō Seichō and others came to the Beijing Zongli Yamen to "kneel for long periods, wailing and pleading with tears of blood," hoping the Qing government would rescue Ryukyu "in consideration of two hundred years of loyal vassal service." Yet the Ryukyuan envoys' desperate pleas for a year yielded no results. Lin Shigong, in extreme grief and indignation, decided to plead for troops with his death, hoping to obtain the Qing government's response to Ryukyu's petition, ultimately committing suicide by cutting his throat for his country.

Hanlin Academy Compiler Lu Tingfu memorialized, proposing to subdue Japan by force to eliminate future troubles. Lu Tingfu had already realized that Japan's aggressive foreign expansion was extremely harmful; if Japan was not effectively and quickly stopped and deterred, Korea would follow Ryukyu's fate, and China would not only be unable to protect its buffer vassal states but would also see its own territory greatly threatened. However, such radical views were not the dominant thinking at the time. Due to internal troubles and external threats, accumulated poverty and weakness, the Qing government had no time or energy to consider the Ryukyu issue. On November 11, 1880, Li Hongzhang memorialized that China could not and was unable to negotiate simultaneously with Russia and Japan; otherwise, it would certainly suffer another diplomatic loss. To counter external pressure, forces must be concentrated so that treaties concluded could avoid greater losses. He persuaded the court with his powerful analysis of the situation, rejecting the "preserve Ryukyu" plan. After Li Hongzhang proposed "delay in agreeing to treaty revision," Japanese negotiator Shishido Tamaki returned home in frustration, the Ryukyu issue was shelved, and the Qing government had no further word on "preserving Ryukyu." In fact, after Japan forced Korea to sign the Treaty of Ganghwa in 1876, the Qing government gradually shifted its attention from Ryukyu to the Korean issue, and the urgency of the Ryukyu issue took second place to Korea. China's suzerainty over Ryukyu existed only in name. The suzerain-vassal relationship was a symbol of the Qing Dynasty's control over the four quarters and display of great power bearing. The suzerain recognized a vassal state's king through investiture, morally assuming responsibility for protecting its security. Generally, the suzerain did not send troops to vassal states; vassal states called the suzerain the "Upper Court" and followed the suzerain's calendar. The Qing government's active weakening of suzerainty marked its abandonment of protecting Ryukyu.

The fall of the Ryukyu Kingdom was undoubtedly a devastating blow to the Ryukyuan people. In the former Ryukyu Kingdom territory, Ryukyuan remnants rose up everywhere, spontaneously organizing armed resistance. Ryukyuan aristocrat Mō Inryō and others organized the "Alliance Party," using extreme means to attack the Japanese occupiers of Ryukyu. Before Ryukyuans could recover from the grief of national destruction, Japanese rulers imprisoned the king, brutally suppressed anti-Japanese forces, established police stations, and monitored the people. To eliminate local resistance, Japanese rulers preserved the backward "concubine service" system that should have long exited the historical stage. Japan's cruel oppression and exploitation aroused Okinawan resistance. In 1893, villagers of Miyako Island launched the "Petition Movement to Abolish the Poll Tax." Soon, the "Okinawa Freedom and Popular Rights Movement" demanding democracy and civil rights also appeared. In 1894, Okinawa Governor Narahara Shigeru, citing "relief for impoverished samurai and industries," took the opportunity to propose developing Somayama. This was strongly opposed by local villagers, who jointly submitted a "Petition to Reject the Somayama Reclamation Permit" to the prefectural government. Jahana Noboru, then Okinawa Prefecture's chief of agricultural and forestry reclamation affairs, was responsible for handling this matter. Deeply influenced by freedom and popular rights ideology, Jahana expressed sympathy for the people's plight after receiving their petition. After on-site investigation, Jahana firmly opposed government development of Somayama, greatly displeasing the Okinawa governor. In 1898, Jahana was forced to resign. The following year, Jahana organized the "Okinawa Club" and "criticized prefectural administration" in his self-published journal "Okinawa Times," calling for "land system reform" and "obtaining suffrage," demanding freedom and popular rights. However, under violent suppression and high pressure from the Japanese government, the Okinawa Freedom and Popular Rights Movement ultimately failed. Jahana was later arrested by Japanese occupiers and died miserably in prison. This movement was ultimately bloodily suppressed by Japanese rulers and ended in failure.

With China's defeat in the First Sino-Japanese War, the Qing Dynasty was unable to raise objections to Japan over the Ryukyu issue, Japan's annexation of Ryukyu became final, and Ryukyuans' hopes for national restoration were dashed. Japan's annexation of Ryukyu put the Qing government in a situation of being attacked on all sides. The Qing government had originally mainly dealt with powerful enemies from the west and north; now it had added an eastern opponent. The Qing ruling group felt unprecedented pressure after losing Ryukyu; their feelings must have been extremely complex.

After the outbreak of the War of Resistance Against Japan, in April 1938, Chiang Kai-shek stated at the Kuomintang's Extraordinary National Congress: "Since the Meiji Restoration, Japan has long had a consistent plan for continental aggression. In the past Sino-Japanese War, it occupied our Taiwan and Ryukyu; after the Russo-Japanese War, it annexed Korea, seized our Lüshun and Dalian, completing the first step of its continental policy..." This was the first clear statement by the highest authority of the Nationalist government on the Ryukyu issue, actually reflecting the aspirations of the Chinese people to recover Ryukyu and wash away the national humiliation of the past century.

Before World War II ended, the Republic of China government had many internal disagreements on how to handle Ryukyu's future, with vacillating and contradictory attitudes on the Ryukyu issue. On January 29, 1942, the ROC Ministry of Foreign Affairs drafted a "Revised Draft of Basic Principles for Resolving Sino-Japanese Issues." The fourth clause of "Principles on Territorial Provisions" in this draft stated: Ryukyu shall be assigned to Japan, but subject to the following two restrictions: (1) No fortifications shall be established, and supervision shall be conducted by a subcommittee of the arms reduction conference; (2) There shall be no discriminatory treatment of Ryukyuan people, and all matters shall be handled according to principles for minority issues. This was the first statement by ROC government officials on Ryukyu's status. However, based on the historical sentiment of traditional Sino-Ryukyuan relations, Chinese domestic opinion was dissatisfied with the government's attitude, and calls to recover Ryukyu grew increasingly loud. Under domestic pressure, on November 3, Foreign Minister T.V. Soong told Chinese and foreign reporters that "after the war ends, China will recover Manchuria, Formosa (Taiwan), and the Ryukyu Islands, and Korea will also gain independence." This was the first formal statement by the Chinese government that China wanted to "recover Ryukyu" after the war, thus opening the curtain on China's demand to recover "Ryukyu."

At 8 PM on November 23, 1943, when Roosevelt and Chiang Kai-shek discussed important postwar matters in Cairo, the Ryukyu issue was mentioned. According to the ROC government's memorandum, Roosevelt took the initiative to mention the Ryukyu Islands, "repeatedly asking whether China wanted the Ryukyu Islands." Chiang Kai-shek replied: "China is willing to jointly occupy the Ryukyu Islands with the United States, ultimately under trusteeship of an international organization with joint management by both countries." Chiang advocated "Sino-American joint management" of Ryukyu, believing that under the premise that China was unable to trustee alone, Sino-American joint trusteeship was the most reasonable proposal at the time.

After the "Chiang-Roosevelt Talks," Chiang Kai-shek acknowledged that he had taken the initiative to propose joint management of Ryukyu with the United States: "The four northeastern provinces and Taiwan with the Penghu Islands should all be returned to China, but Ryukyu can be entrusted to international organization for Sino-American joint management—this was proposed by me." Chiang Kai-shek recorded the reasons for this proposal, mainly based on three considerations: first, to put the Americans at ease; second, Ryukyu had already belonged to Japan before the First Sino-Japanese War; third, having this area jointly managed by the United States was better than having it exclusively ours. Chiang Kai-shek's consideration of Ryukyu's attribution was not a hasty response. Before going to Cairo, he recorded in his diary on November 15, 1943: Ryukyu's historical position in our country differs from Taiwan's, and as Ryukyu was a kingdom, its status was equal to Korea's, so this proposal decided not to raise the Ryukyu issue, while the Siam independence issue should be raised by us. The background of Chiang Kai-shek's proposal to Roosevelt for Sino-American joint management of Ryukyu at the Cairo Conference was quite complex, "with moral factors, power factors, and strategic considerations all playing a role."

On November 27, 1943, the day of the Cairo Conference, Chiang Kai-shek, U.S. President Roosevelt, and British Prime Minister Churchill jointly issued the Cairo Declaration in Cairo, clearly stating: "Japan shall be stripped of all the islands in the Pacific which she has seized or occupied since the beginning of the First World War in 1914, and that all the territories Japan has stolen from the Chinese, such as Manchuria, Formosa, and the Pescadores, shall be restored to the Republic of China." However, the positions of China, the United States, and Britain on the Ryukyu issue were not included, nor was Ryukyu's future status mentioned in the subsequent Yalta Agreement or Potsdam Proclamation. However, Article 8 of the Potsdam Proclamation stipulated: "The terms of the Cairo Declaration shall be carried out and Japanese sovereignty shall be limited to the islands of Honshu, Hokkaido, Kyushu, Shikoku and such minor islands as we determine."

At a White House meeting on January 12, 1944, Roosevelt, recalling his conversation with Stalin, said that Stalin had also indicated "he was very familiar with Ryukyu's history, he completely agreed that Ryukyu belonged to China and should be returned to China, and that administrative authority over all islands under Japanese control should go to the United Nations." This shows that the Soviet leader at the time also recognized Ryukyu's return to China. However, at the Tehran Conference, Stalin made no relevant statement on this. From the above, based on wartime Allied opinions, Ryukyu should be separated from Japan after the war; even if not handed over to Chinese management, it should be jointly trusteed by China and the United States, with its ultimate direction being independence or autonomy.

From when the Pacific War was still ongoing until the major shift in policy toward Japan in 1948, various departments of the U.S. government had been conducting in-depth and extensive research on postwar disposition of Okinawa, proposing various plans and opinions. However, national-level policy toward Okinawa remained in intense discussion and flux. Among them, the military represented by the Army Department, Navy Department, and Joint Chiefs of Staff, from a military strategic perspective, had requirements for Okinawa ranging from the most radical U.S. possession to "strategic trusteeship" to "general trusteeship"—in summary, hoping to separate Okinawa from the Japanese mainland, achieve U.S. military occupation, and make it the most important U.S. military base in the Far East. In contrast, the State Department (represented by the Far East Bureau), from political and diplomatic perspectives, hoped to return it to Japan after completing demilitarization and democratization of the region. The opposition between the two sides kept U.S. policy toward Okinawa long undecided. This situation allowed the military responsible for actual occupation to basically implement rule according to its own views. During this period, on January 29, 1946, the United States, through Supreme Commander for the Allied Powers Directive No. 677, achieved the separation of the Amami, Okinawa, Miyako, Yaeyama, and other island groups from the Japanese mainland.