By Anthony Marco and Nils Peterson*
On September 13th, 2025, a Chinese Coast Guard (CCG) vessel entered the restricted waters around the Republic of China’s (ROC) Dongsha Atoll, also known as the Pratas Island, located approximately 400 kilometers southwest of the ROC’s main island of Taiwan. The CCG intrusion prompted a swift response from the ROC’s Coast Guard Administration (CGA), which consisted of a CGA vessel chasing the CCG intruder from the area. (From: The Center for International Maritime Security.)
Over the next four days, the CCG mounted four separate incursions into the restricted waters around Dongsha, a worsening symptom of a wider Chinese Communist Party (CCP) maritime gray zone campaign against the ROC in which the CCG has a prominent tool of coercion.
This article employs the Office of the Director of National Intelligence’s (ODNI) definition of gray zone coercion, the “deliberate use of coercive or subversive instruments of power by, or on behalf of, a state to achieve its political or security goals at the expense of others, in ways that exceed or exploit gaps in international norms but are intended to remain below the perceived threshold for direct armed conflict.”
The ongoing coercion by the Chinese Coast Guard (CCG) aims to erode the ROC’s sovereignty by sending a message to the international community that the CCP has both the capability and the will to exert control over the waters near Taiwan, but this activity also threatens the United States’ national security interests. It is in America’s interest that the ROC remains a political entity distinct from the People’s Republic of China (PRC) for two primary reasons. First, at the operational level, Taiwan is a key maritime terrain in the First Island Chain or FIC, forming the foundation of American strategy in East Asia to counter the CCP’s territorial revisionist ambitions from a geographic standpoint. Second, at the strategic level, a CCP takeover of Taiwan would severely undermine the confidence of key regional and treaty allies, such as Japan and the Philippines, in the United States’ ability to defend them against further CCP aggression.
In the immediate term, CCG gray zone activity also displays the potential to endanger hard US economic interests by threatening major sea lines of communication (SLOCs) that enter the Taiwanese main island’s major ports at Kaohsiung, Keelung, Mailao, Taichung, and Taipei. Taiwan produces over 90% of advanced semiconductor chips and is the seventh-largest merchandise trading partner of the United States, underscoring the importance of SLOCs entering Taiwan for American economic welfare.
If the PRC expands its gray zone maritime activity in a manner that threatens SLOCs, potentially leading to a maritime quarantine of Taiwan, this presents the US and its Pacific partners with the decision of whether to employ a military response. Recognizing, at a minimum, the economic damage and escalatory risks tied to potential CCP attempts at threatening the vitality of SLOCs, it behooves American policymakers to take steps to deter the expansion of this CCG-spearheaded maritime gray zone campaign.
The Nature of the CCG Threat
Over the past two years, the CCP has taken substantial steps to intensify its maritime gray zone campaign in ROC waters. In February 2024, a Chinese motorboat violated Kinmen’s restricted waters, prompting a CGA-mounted chase, which resulted in the deaths of two Chinese nationals when their boat capsized. The PRC has since used the incident to justify mounting a concerted effort to undermine ROC territorial sovereignty over the Kinmen Islands and Matsu Islands–located four milesand six miles off the coast of the People’s Republic of China, respectively–by routinely dispatching CCG vessels that violate the islands’ restricted waters: CCG activity reached a total of 85 violations around Kinmen in September 2025.
While Kinmen and Matsu lie just a short boat ride away from the PRC mainland, the CCP’s effort to undermine ROC territorial sovereignty has more recently extended to Dongsha. According to the CGA, an “unprecedented” flotilla of Chinese fishing vessels, numbering six “mother ships” and 29 “smaller boats,” entered restricted ROC waters around Dongsha on February 15th, 2025, prompting a swift response from local CGA vessels.
During this incident, a CCG vessel violated Dongsha’s restricted waters by attempting to intervene in the CGA’s law enforcement response. Since this incident, the CCG has sought to normalize this activity with consistent intrusions into the waters around Donghsa. Although Dongsha, like Kinmen and Matsu, lies on the ROC periphery, its recent targeting by the CCG is demonstrative of a graduated coercive campaign.
The CCG has also recently demonstrated its capacity to perform in a role that is specifically more dangerous to US interests. In a noticeable departure from past practice, the CCG, in what appears to be a PRC attempt to hybridize a potential blockade, debuted in PLA live-fire exercises around Taiwan during Joint Sword 2024-A in May 2024. This was followed up by Joint Sword 2024-B in October 2024, featuring approximately seventeen CCG vessels circumnavigating the Taiwanese main island as part of coordinated blockading drills with the PLAN.
During Joint Sword 2025-B, this year’s inaugural exercises in February, the CCG played a higher profile role that included carrying out mock vessel boardings and inspections–suggestive of potential actions that would interdict commercial shipping, a cardinal feature during a blockade or gray zone “quarantine”–in addition to violating, for the first time, the Taiwanese main island’s 24 nautical mile contiguous area.
Although the CCP has not yet made a serious effort to dispute SLOCs to Taiwan, its multi-pronged gray zone activities suggest an intensifying trend that makes this a growing concern for the future. One potential route entails mounting infrequent CCG patrols of SLOCs that evolve into routine patrols, activities the CCP has attempted to normalize in other places through consistent effort, justified under the auspices of a contrived or provoked maritime incident. Patrols could evolve into the boarding and inspection of international commercial vessels, setting the conditions for a partial or full and temporary or indefinite maritime quarantine of the main island.
From a US standpoint, whether such gray zone maritime activity forms a deliberate, calibrated irregular warfare strategy to achieve unification non-kinetically or broadly aims to isolate Taiwan economically and politically, wherever and whenever the PRC can, any attempt to threaten SLOCs in this manner jeopardizes hard US and partner-nation interests. Thus, taking preventive measures to preserve SLOCs prior to PRC efforts to sever them is necessary, especially since attempting to roll back the latter’s efforts after the fact is more difficult and could risk a more dangerous escalation.
Policy Recommendations
The US Government (USG) should pursue a nested set of policy goals to address the CCG threat to American interests. At the operational level in the immediate term, the objective should be to deter CCG activity that would threaten American SLOCs. At the political level in the immediate term, the USG should accept the unpleasant reality that the existing CCG activity erodes ROC sovereignty, as it lacks the capacity to substantially roll back CCG presence. At the operational and political levels in the future, the objective should be to have a coalition prepared to deter a PRC maritime quarantine of Taiwan.
These policy goals rest on three key assumptions; if any of these is invalidated, the recommendations would no longer hold. First, the CCP does not deploy CCG assets in such numbers that they overwhelm our capacity to defend key SLOCs. Second, the CCP continues its salami-slicing strategy to degrade the operational environment around Taiwan, which involves minimizing direct confrontation between the PLA and foreign coast guard assets in waters that the party views as its own. Third, the CCP leadership thinks it still has time to achieve its political objective to gain control of Taiwan and therefore decides it does not now need to launch a maritime quarantine, blockade, or invasion.
The ROC, on its own, will likely struggle to preserve SLOCs. During a 2024 House Subcommittee Hearing on Transportation and Maritime Security, Senior Policy Researcher at the RAND Corporation, Captain Eric M. Cooper, USCG (Ret.), estimated that there are a total of 700 CCG vessels operating in the Indo-Pacific. The entirety of the CCG’s complement is not dedicated to gray zone activity against Taiwan, but it has a growing presence deep in the South China and East China Seas. The CGA, on the other hand, maintains a smaller, but not insignificant force of approximately 250 vessels. Since 2018, the CGA has implemented a ten year indigenous shipbuilding program, with a target goal of 141 newly constructed vessels, but it remains and will remain overmatched by the sheer quantitative advantage retained by the CCG. Thus, it is unreasonable to expect the CGA to adequately deter potential CCG activity that jeopardizes SLOCs.
Recognizing the vulnerability of SLOCs, the US Coast Guard (USCG) is uniquely positioned to preserve them. Already, throughout the Indo-Pacific, the USG maintains a series of bilateral Maritime Law Enforcement Agreements (MLEA) that authorize the USCG to carry out activities such as conducting legally protected patrols to help safeguard a partner country’s maritime security.
Traditionally, bilateral MLEAs stipulate that the USCG dispatch personnel and or vessels to assist in maritime law enforcement within a partner country’s territorial waters (12 nautical miles), contiguous zone (24 nautical miles), and EEZs (200 nautical miles). For example, as provisioned under a bilateral MLEA, the USCG boarded six vessels illegally fishing within the Cook Islands’ EEZ this past June. The USCG also conducts maritime law enforcement exercises with regional partner countries.
In June 2024, the USCG trained alongside the Philippine Coast Guard (PCG) in the South China Sea to buttress the latter’s law enforcement and search and rescue capabilities. The USCG has also scaled up exercises in the Indo-Pacific region into trilateral events: in June 2025, the USCG, PCG, and Japanese Coast Guard (JCG) participated in drills outside Japan’s territorial waters for the first time. According to the senior participating USCG officer, Captain Brian Krautler, “By operating together, we strengthen our collective forces, ensuring readiness against threats to maritime safety and security.”
With the specific intent of maintaining SLOCs entering Taiwan, the USCG should seek to replicate similar activity with the CGA as would be provisioned in a bilateral MLEA. The USCG already has a pre-existing cooperative relationship with the CGA that is guided by a Memorandum of Understanding (MOU), signed between the American Institute in Taiwan (AIT) and the Taiwan Economic and Cultural Representative Office (TECRO) in March 2021. Under this MOU, the USCG and CGA formed a Coast Guard Working Group (CGWG) to establish a common understanding of maritime security priorities and advance cooperation between the USCG and CGA. In addition to the dialogues within the CGWG, instances of security cooperation have occurred. For example, in 2024, the USCG dispatched an International Port Security (IPS) Program team to Taiwan to exchange knowledge with CGA officials regarding how to enhance maritime cybersecurity and general port security.
Despite these positive developments, current USCG and CGA cooperation is inadequate, with it being limited to informal bilateral talks, workshops, and occasional practice sharing. Thus, the MOU should be updated to deepen security cooperation or an unofficial agreement, akin to a bilateral MLEA, established that extends USCG authorities in ROC waters, specifically granting the USCG the ability to conduct patrols along SLOCs, sending a clear message to the CCP that the US will protect its interests.
In line with past practice, whenever the US deepens security cooperation with the ROC, the CCP will likely vehemently protest such a move; however, given the recognizable and public economic interests at stake in preserving SLOCs, the USG should frame USCG presence patrols in Taiwanese waters within the context of that specific end rather than communicating an intent to buttress ROC claims to sovereignty, although this would be an undeniably favorable byproduct.
It must be acknowledged that, compared to the CCG, the current and near-term potential force posture of the USCG in the region is problematic. Presently, the USCG has eight vessels forward deployed in the region and possesses another 79 vessels capable of serving in the region, but this would practically amount to the USCG’s entire inventory of high seas vessels. Despite this modest vessel count, the USCG could afford to apportion a couple of cutters and a handful of smaller craft, based on existing deployments in the Indo-Pacific region, communicating the USG’s resolve concerning the preservation of SLOCs.
A comprehensive analysis is warranted to assess the impact this deployment would have on other USCG priorities in the theater. Still, such deployments would communicate the USG’s resolve to preserve SLOCs. This is especially the case due to the escalatory risks the CCP would incur by contemplating a confrontation with a USCG vessel performing its duties. The USG could also establish a shiprider agreement, a type of MLEA, with the CGA, permitting USCG personnel to board CGA vessels: the USG maintains twelve such agreements with regional partners such as Papua New Guinea and the Republic of Vanuatu. Although typically partner force personnel board USCG vessels, USCG personnel have boarded Royal Navy vessels under a shiprider arrangement, which can be replicated with the CGA.
Moreover, the USG should seek ways to internationalize any USCG efforts to preserve SLOCs entering Taiwan. USCG Captain (Ret.) Eric Cooper has made compelling arguments for the establishment of a multilateral maritime law enforcement task force in the form of the US-led Bahrain Combined Maritime Force (CMF). Headquartered in Bahrain and consisting of 46 participating countries, the CMF maintains maritime security in major waterways around the Middle East. Organizing a task force akin to a CMF with the aim of preserving Taiwan’s SLOCs could include countries like Japan and the Philippines, especially when considering these two countries’ significant economic interests linked to these SLOCs and their recent combined participation in USCG-led exercises.
If these recommendations are implemented, the following would be benchmarks to measure success: In the immediate future, the continued absence of CCG vessels in key SLOCs. In the longer term, a stable rotational presence of up to three USCG cutters and between five and ten smaller craft regularly operating in the Indo-Pacific, particularly in areas proximate to Taiwan, in conjunction with a CMF-style task force.
The deteriorating security situation around Taiwan due to the CCP-initiated gray zone coercion shows no signs of improvement in the near future. In addition, the United States no longer enjoys being the unrivalled seafaring power in East Asia. In this security environment, the creative employment of USCG assets and personnel in combination with regional partner countries becomes an important policy pathway toward achieving American national interests.
*Anthony Marco is a First Lieutenant in the U.S. Army and holds a BS from the United States Military Academy at West Point and an MA from Reichman University as an Anna Sobol Levy Scholar. He also serves as a special advisor on the Irregular Warfare Initiative’s Proxies and Partners Special Project.
*Nils Peterson is a Marshall Scholar studying for an MA in Taiwan Studies at the School of Oriental and African Studies and holds a BA in History and Chinese from the University of Wisconsin-Madison. He previously led the China Team at the Institute for the Study of War as a War Studies Fellow.
