China has deployed on average two Coast Guard cutters per month east of Taiwan since June, after Japan and the Philippines announced plans to define their overlapping maritime border in the region. The appearance of those vessels marks the first time such patrols have been reported in the area in data going back to January 2025.      Patrols in these waters covered a vast area of 27,100 square nautical miles — more than twice the size of Taiwan — based on Bloomberg calculations using ship-tracking data. Ships stayed 30 nautical miles from the island’s eastern coast, remaining outside Taiwan-claimed waters.   Controlling the east would become essential to enforcing an effective blockade of Taiwan during a Chinese invasion of the island. Disrupting shipping off the Pacific coast would have global implications for commodities. Vessels ferrying oil, gas, iron ore and agricultural products made 527 transits through the east in June, exceeding the 420 through the generally busier Taiwan Strait, according to MarineTraffic data.  

“If the Taiwan Strait is the front door, the eastern waters have often been treated as the back door,” said Jing Ge, instructor at Florida International University’s politics and international relations department. “Beijing wants to demonstrate this back door is no longer uncontested.”

While the Taiwan Strait handles almost half the world’s container fleet, the island’s eastern coast holds strategic importance by forming a maritime link with the Philippines and wider Pacific. Sea lanes in the area lead to key ports and military facilities, where the US and its regional allies could deliver supplies, while its deeper waters are ideal for submarines and undersea surveillance.   China’s Coast Guard has described such deployments as “routine law-enforcement” patrols, and has pledged to strengthen patrols to safeguard Beijing’s maritime rights. China has in the past also conducted military drills, including in this area, to rehearse encircling Taiwan, the self-governed island the Communist Party considers its own despite never having ruled it.   China’s activity is an attempt to “leverage ‘law enforcement patrols’ to establish a new normal for its maritime presence in the waters east of Taiwan,” the Taiwan Coast Guard Administration said in an email. Vessels have been dispatched in a timely manner in response, it added.  

The US has called China’s actions “deeply destabilizing.” Despite that opposition, China’s Coast Guard announced last week it had deployed a new set of vessels east of Taiwan, sustaining its presence in the area. 

The role of China’s Coast Guard has moved beyond traditional law enforcement in recent years. That was laid bare by the introduction of a Coast Guard Law in 2021, which expanded the agency’s reach by authorizing it to “take all necessary measures, including the use of weapons” to protect what Beijing defines as China’s sovereignty. 

Its new operations around Taiwan started on June 1, when China’s Coast Guard deployed two large patrol cutters — the 5,000-ton Daishan and the 3,000-ton Baita — to waters east of the island. Those vessels were previously used around the East China Sea, including the Japanese-controlled Senkaku islands, which China also claims and calls the Diaoyus.   Days earlier, Japan and the Philippines had announced plans to start negotiations to delimit their sea boundaries, as part of broader efforts from the two US allies to deepen their partnership. China opposed the talks, saying they’d interfered with its own maritime claims in that region.   “Beijing is using the joint statement issued by Japan and the Philippines as a pretext for greatly expanding its presence in these waters,” said Ryan Martinson, assistant professor at the China Maritime Studies Institute of the US Naval War College.  Later in June, China sent larger law enforcement ships, the 10,000-ton Haixun 09 and the 6,600-ton Haixun 06, to circle Taiwan. That rare multi-agency operation included China’s largest deep-sea survey ship and a rescue vessel.  

During their five-day voyage, the vessels for the first time questioned foreign commercial ships passing along Taiwan’s Pacific coast. According to Chinese state media, the ships also “inspected” 198 passing vessels during the mission to reinforce traffic-control capabilities. It was unclear what the report meant by “inspected.”   “If those interactions become routine, the next question is whether Chinese authorities begin to request more information,’ said Zack Liao, political risk analyst at UK-based think tank China Strategic Risks Institute. “After that, whether they issue navigational instructions.”

US-based independent monitor Armed Conflict Location & Event Data has separately reported “a significant increase in research vessels operating at unusually slow speeds east of Taiwan” near undersea communications infrastructure.   China kept up the pressure by sending two more Coast Guard cutters to relieve the Daishan and Baita after a month in the area. That was described by a US congressional commission as Beijing’s way to establish a continuous presence. 

“Using the CCG rather than the PLA Navy avoids military confrontations and allows Beijing to portray these activities as law enforcement while establishing the persistent presence necessary for a future blockade,” said the US-China Economic and Security Review Commission.

As the activity ramped up, Taiwan held military exercises in mid-July on Orchid and Green Islands, off its southeastern coast, for the first time in three decades. Weeks later, China staged passing exercises with Indonesia in the area, the first time Beijing has announced training with another country in the eastern waters.   China’s push to establish a presence east of Taiwan ultimately puts pressure on the US to respond, analysts say.     “What Beijing is testing east of Taiwan is whether it can gradually rewrite expectations about who governs navigation and maritime order in the Western Pacific,” said the China Strategic Risks Institute’s Liao. “That means the response should also be international.”