The China Coast Guard's Transition to a Regular Patrol Regime in the Waters East of Taiwan: Legal and Strategic Implications

Executive Summary

Since July, China Coast Guard (CCG) patrols in the waters east of Taiwan have entered a phase of normalization. The number of CCG vessels near the main island of Taiwan rose by 37.5% year-on-year, while vessel presence surged by 3,800% in the eastern waters where new patrols were initiated. Rather than rejecting the UN Convention on the Law of the Sea (UNCLOS), China has chosen to assert its jurisdiction over its exclusive economic zone (EEZ) and continental shelf using UNCLOS terminology. This approach shares the same legal structure as its nine-dash line logic in the South China Sea, making procedural rebuttals by third countries difficult. Combined with the tactics of silence and ambiguity observed during the Han Kuang exercises in August, traditional early warning indicators have lost their utility. Consequently, the cumulative, event-independent normalization of gray-zone pressure is assessed as the most likely scenario. This issue simultaneously intersects with key axes of US-China strategic competition—namely military rivalry in the Taiwan Strait and the Western Pacific—regional dynamics and disputes concerning sea lines of communication (SLOCs) and freedom of navigation, and alliance and multilateral security frameworks linked to the US-ROK-Japan deterrence posture. Rather than preparing for specific conflict scenarios, South Korea needs a decentralized risk-management approach predicated on absorbing a constant risk premium, alongside establishing its own monitoring system to compare these developments with the situation in the West Sea.

I. Issue Analysis

The China Coast Guard's Transition to a Regular Patrol Regime in the Waters East of Taiwan

1. Background and Progress of the Issue

Chinese pressure surrounding the Taiwan Strait is not a new phenomenon. Since Deng Xiaoping adopted the peaceful unification line in 1979, Beijing has maintained the logic of keeping cross-strait relations manageable to foster its own economic development [6][8]. This premise began to falter during the 2019 Hong Kong National Security Law crisis. Watching Beijing's harsh crackdown on Hong Kong protesters, Taiwanese public opinion shifted drastically. Support for gradual independence doubled from 12.8% in 2018 to 25% in 2019 [6][8]. Conversely, support for unification dropped from 12.8% to the 6–7% range over the same period [6][8]. Since then, Chinese military activities around Taiwan have become a routine instrument of pressure [8].

The shift observed since July of this year is that the center of gravity of this pressure has expanded from the western strait to the eastern waters. *The Diplomat* assessed that this is "partially linked to recent maritime incidents in the East China Sea," but noted that, independent of this, there is a clear trend of the People's Liberation Army (PLA) unilaterally ramping up the scale and intensity of its activities in the airspace and waters east of Taiwan [1]. The waters east of Taiwan had previously seen rare regular activity by the China Coast Guard compared to the western strait. The normalization of patrols in this area is an event that forces a fundamental reassessment of Taiwan's defense concept.

2. Current Situation

In August, official Chinese vessel activities around Taiwan reached 118 incidents, marking a record high for the third consecutive month [3][8]. This period coincided with a gap in US aircraft carrier presence in the Western Pacific due to the prolonged conflict involving Iran [3][8]. Taiwan's Ministry of National Defense assesses that China utilized this gap as an opportunity to test in practice the limits of the United States' ability to respond to two theaters simultaneously [3][8].

Previously, large-scale military aircraft incursions or the size of military exercises served as early warning indicators. However, during the Han Kuang exercises in August, China responded with silence and brief, dismissive commentaries instead of large-scale counter-exercises, leading to assessments that these indicators are losing their utility [3][6][8]. Instead, the routine entry of vessels has itself emerged as the primary form of pressure. This unpredictability is interpreted as a tactic to deliberately obscure the timing and intensity of Beijing's response, thereby complicating the strategic calculus for both Taiwan and the United States [3][6][8].

Testimony from Taiwan Coast Guard Captain Hsu Wei-hung supports this shift on the ground. Having served for over 20 years, he identified this year as the worst, stating that he encounters Chinese vessels on almost every mission. According to his observations, Chinese vessels increasingly resemble warships and attempt to breach Taiwan's defensive lines through maneuvering and speed adjustments. An analysis by the CSIS Futures Lab indicates that the daily average number of China Coast Guard vessels in the waters near the main island of Taiwan increased by 37.5% compared to the previous summer, while surging by 3,800% over the same period in the eastern waters where patrols newly commenced.

During the same period, the Taiwan Coast Guard moved to strengthen its own capabilities. The Anping-class patrol vessel *Chijin* conducted a live-fire test of the Hsiung Feng III (HF-3) supersonic anti-ship missile, successfully striking a decommissioned frigate 100 kilometers away. It is highly unusual for a civilian law enforcement agency to publicly conduct such armed training, which is interpreted as a sign of deepening integration between the Taiwan Coast Guard and Navy [7]. Foreign diplomatic envoys stationed in Taiwan have also publicly expressed concern that the very rules of maritime order are being tested [9].

3. Key Actors and Positions

China's Ministry of Foreign Affairs and the Taiwan Affairs Office (TAO) of the State Councilargue that China's EEZ and continental shelf extend to the waters east of Taiwan based on domestic and international laws, including UNCLOS. The patrols are framed not as a rejection of UNCLOS, but as an assertion of Chinese jurisdiction using UNCLOS terminology. China has also employed harsh rhetoric regarding Taiwan-Philippines maritime cooperation. TAO spokesperson Zhu Fenglian criticized the Democratic Progressive Party (DPP) authorities for "betraying national principles in an extremely despicable manner" after a decommissioned Taiwanese coast guard vessel transferred to the Philippines was converted into a Philippine law enforcement ship [10]. The *Global Times* sought to deter Japanese involvement by arguing that the Philippines' provocations against China were independent of Japan, while framing Japan's support for the Philippines as a "strategic intent to break free from the constraints of its pacifist constitution" and an effort to play the role of a "regional proxy for the US-Japan alliance" [14].

The Taiwanese Governmenthas adopted a dual-track approach of exercising restraint to avoid provocation while refusing to back down. In an interview ahead of the US-China summit, Vice President Hsiao Bi-khim stated that Taiwan would not provoke but would also not compromise on freedom and democracy. The Taiwan Coast Guard's live-fire missile drills and its enhanced integration with the Navy are physical manifestations of this stance [7]. Simultaneously, Taiwan is incorporating contingency scenarios into its disaster preparedness drills. A national disaster drill conducted in Taitung used a magnitude 7.3 earthquake as its baseline scenario—assuming damage to 43 bridges and 1,800 buildings, alongside 63 casualties—and expanded the participation of regional and international partners to test coordination under conflict-like conditions [11].

The Philippine Governmentreaffirms its commitment to the One-China policy while maintaining its position to continue economic and cultural cooperation with Taiwan [18]. Local observers point out that this carries the risk of adding the Taiwan issue to the South China Sea disputes as another point of friction with China [12]. Indeed, as close encounters between Philippine civilian vessels and the China Coast Guard increase, some analyses suggest these are provocations linked to Manila's push to militarize Palawan [13].

The United Statesfaces growing controversy surrounding its policy of strategic ambiguity. As the Trump administration repeatedly made remarks shifting the blame for Taiwan Strait tensions onto Taiwan, assessments emerged that the long-standing policy of strategic ambiguity has effectively lost its direction [4][5]. The Brookings Institution pointed out that Trump's demands for Taiwan to "cool down" and his questioning of whether it makes sense to fly 9,500 miles to fight a war actually ended up adopting Beijing's preferred framing [5].

Japanhas increased its involvement in Western Pacific affairs through its support for the Philippines and statements regarding Taiwan, which in turn has drawn strong pushback from China [14].

4. Key Issues

The first issue is the clash of legal logic. While China asserts its jurisdiction within the framework of UNCLOS, the US-led principle of freedom of navigation opposes the imposition of transit conditions based on the very same convention. This setup, where two competing interpretations of the same international legal framework clash head-on, is now playing out in the waters east of Taiwan.

The second issue is China's pattern of response to maritime boundary negotiations between third countries. Beijing's practice of defining boundary delimitation discussions between Japan and the Philippines as an infringement on its own jurisdiction and responding with physical demonstrations of force is a precedent that warrants close attention, as it could be applied to other maritime areas in East Asia in the future.

The third issue is the potential for peacetime regular presence to transition into an operational foundation during a contingency. The waters east of Taiwan hold strategic significance as both a corridor for external assistance and an approach route for US and Japanese forces. Whether the continuous presence of the China Coast Guard serves as a preliminary step for blockade or quarantine operations is a key variable in military assessments.

The fourth issue is the neutralization of early warning indicators. As continuous vessel activity and unpredictable response patterns replace large-scale exercises or massive aircraft incursions as the primary mode of pressure, it is becoming increasingly difficult for existing warning systems to detect the threshold of a crisis [3][6][8]. Regardless of how the Taiwan issue is addressed at summits, the core asymmetry of this situation lies in the fact that the creation of *faits accomplis* at sea is proceeding on an independent timeline.

II. In-Depth Analysis

The China Coast Guard's Transition to a Regular Patrol Regime in the Waters East of Taiwan

1. Root Cause Analysis

The ostensible trigger for this patrol normalization is the maritime conflict involving Japan and the Philippines. *The Diplomat* noted that the patrols in the waters east of Taiwan, which began after July, are "partially linked to recent maritime incidents in the East China Sea" [1]. The Philippines continues to clash with the China Coast Guard in the South China Sea, as seen in the September collision incident involving the Xianbin vessel [14]. It was also revealed that Taiwan donated a decommissioned coast guard vessel to the Philippines, which was converted into a law enforcement ship [10]. The Taiwan Affairs Office of China's State Council strongly criticized this, defining it as a "despicable act that betrays national principles" [10]. The Philippine Department of Foreign Affairs reaffirmed its adherence to the One-China policy while maintaining its stance to continue economic and cultural cooperation with Taiwan [18]. China is exploiting this gap as grounds to define Taiwan-Philippines cooperation as an infringement on its core interests [12].

However, the structural causes run deeper than these surface-level triggers. Independent of the situations involving the Philippines and Japan, the PLA has unilaterally scaled up the size and intensity of its activities in the airspace and waters east of Taiwan [1]. In other words, maritime conflicts involving third countries serve as a pretext to justify the patrols east of Taiwan, rather than being the sole cause of their initiation. This aligns with a trend foreshadowed during the Han Kuang exercises in August. At that time, China eschewed large-scale counter-exercises, offering only silence and brief, dismissive commentaries, thereby transitioning to a "unilateral ambiguity tactic that renders the timing and intensity of its response entirely unpredictable" [3][6][8]. The patrols in the waters east of Taiwan represent a spatial expansion of this tactic, transplanting the grammar of gray-zone pressure accumulated in the western strait directly to the east.

The gap in US power deployment in the Western Pacific also coincided with this timing. In August, when US aircraft carrier forces were absent from the region due to the prolonged conflict involving Iran, official Chinese vessel activities around Taiwan reached 118 incidents, marking a record high for the third consecutive month [3][8]. Taiwan's Ministry of National Defense assesses that China utilized this as an opportunity to "test in practice the limits of the United States' ability to respond to two theaters simultaneously" [3][8]. The Trump administration's apparent acceptance of Beijing's framing on the Taiwan issue may have also influenced this calculation. Trump repeatedly made remarks suggesting that Taiwan was the source of tension, and questioned whether it was reasonable for the US military to travel 9,500 miles to fight for Taiwan [5]. The uncertainty of these signals from Washington is what prompted foreign envoys in Taiwan to warn that "the rules of the game at sea are being challenged" [9].

2. Structural Context

Legal Structure: The logic of China's Ministry of Foreign Affairs does not reject UNCLOS; rather, it asserts Chinese jurisdiction using the language of UNCLOS. This is evident in its claims that its EEZ and continental shelf extend to the waters east of Taiwan, and its framing of the patrols as a "legitimate exercise of jurisdiction to maintain maritime order and regional stability." This shares the exact same structure as its nine-dash line claims in the South China Sea—redefining the interpretation of international legal texts to its own advantage without outright rejecting their wording. The same pattern is repeated in the case of the Philippines. Observations that it is becoming increasingly difficult for Philippine civilian vessels to conduct fishing and humanitarian missions [13] demonstrate how China backs its legal jurisdictional claims with physical close-proximity operations. The waters east of Taiwan have now become an arena where these two interpretative frameworks clash head-on.

Military and Security Structure: The waters east of Taiwan hold a strategic weight no less than that of the western strait, serving as a vital corridor for Taiwan to receive external assistance and an approach route for US and Japanese forces during a contingency. The Taiwan Coast Guard's live-fire test of the Hsiung Feng III supersonic anti-ship missile, which struck a decommissioned frigate 100 kilometers away, reflects this threat perception [7]. It is highly unusual for a civilian law enforcement agency to make such armed training public, and experts interpret this as a sign of deepening coast guard-navy integration [7]. Taiwan's incorporation of scenarios responding to multi-system failures during a contingency—going beyond simple earthquake response—into its regional disaster prevention drills in Taitung, along with expanding the participation of regional and international partners, falls under the same context [11]. The core issue within this structure is whether the peacetime continuous presence of the coast guard effectively establishes a pre-positioned foundation for blockade or quarantine operations during a contingency.

Alliance Structure and the Dilemma of Extended Deterrence: The state-run *Global Times*' vehement reaction to a New Zealand naval vessel transiting the Taiwan Strait, calling it "playing with fire" [17], alongside its characterization of Japan's support for the Philippines as an "expression of ambitions to revive militarism" [14], demonstrates China's repeated use of logic that defines third-party involvement as an infringement on its core interests. This logic could similarly be applied to US-ROK-Japan trilateral cooperation or freedom of navigation operations conducted by the Quad. The uncertainty surrounding the Trump administration's remarks on Taiwan [5][15] is a factor forcing regional allies to reassess their own deterrence postures. Japan's first-ever overseas live-fire test of an anti-ship missile during its support for the Philippines [16] is one example of this reassessment.

3. Historical Precedents and Comparison of Similar Cases

The archetype of this case is the "salami-slicing tactics" that China has repeatedly employed in the South China Sea. At Scarborough Shoal and Mischief Reef, China used its coast guard and maritime militia to accumulate physical presence before solidifying it as a *fait accompli*. The same sequence is observable in the waters east of Taiwan: first, increasing the frequency of patrols, and once they become routine, retroactively justifying them through legal jurisdictional claims. However, where this case differs from the existing South China Sea pattern is the vehicle for its pretext. While direct disputes with the Philippines and Vietnam served as the pretext in the South China Sea, in the waters east of Taiwan, the mere initiation of maritime boundary negotiations between third countries—specifically Japan and the Philippines—is reinterpreted as an infringement on China's own jurisdiction [1]. This pattern of defining third-party negotiations as a challenge to itself and responding with physical presence warrants attention, as it represents a precedent that could be applied to the East China Sea or the West Sea in the future.

A comparison with the Han Kuang exercises in August is also instructive. At that time, China chose silence instead of the predictable response of a large-scale counter-exercise [3][6][8]. The normalization of patrols also belongs to the same tactical lineage, in that it was designed as a constant baseline pressure rather than a reaction to a specific event. Both cases share the common goal of neutralizing the early warning indicators that Taiwan and the United States have relied upon—namely, visible signals such as large-scale military aircraft incursions or the scale of military exercises [3][6][8].

4. Key Variables Shaping Future Developments

The first variable is how the Taiwan issue is handled at the US-China summit. Vice President Hsiao Bi-khim's statement that Taiwan "will not provoke but will not compromise on freedom and democracy" reflects Taipei's assessment that the creation of *faits accomplis* at sea will continue regardless of the summit's outcome. Even if the Taiwan issue is temporarily patched over at the summit, the normalization of coast guard patrols is highly likely to proceed on a separate track.

The second variable is whether the deployment of US forces in the Western Pacific returns to normal. Whether the aircraft carrier gap caused by the prolonged conflict involving Iran is resolved, and whether confidence in the US capability to respond to two theaters simultaneously is restored, are variables that will directly influence China's adjustment of its pressure intensity [3][8].

The third variable is whether maritime boundary negotiations between Japan and the Philippines make actual progress. As these negotiations advance, China will have a greater incentive to use them as a pretext to justify and intensify its patrols in the waters east of Taiwan [1][12].

The fourth variable is the pace of integration between the Taiwan Coast Guard and Navy. If the deepening integration demonstrated by the HF-3 live-fire test [7] continues, the threshold for peacetime coast guard standoffs to escalate into paramilitary conflicts will lower. This is an indicator that South Korea should also reference when interpreting Chinese maritime activities in the West Sea. The manner in which legal jurisdictional claims are combined with physical presence, along with the pattern of neutralizing early warning indicators, is an analytical framework that can be similarly applied to cases in the West Sea.