China has sharply expanded coast guard operations in the Pacific Ocean east of Taiwan, extending pressure beyond the Taiwan Strait into waters considered critical to the island’s wartime supply routes and communications with the United States and its allies.
China has deployed an average of two coast guard cutters a month east of Taiwan since June, the first such patrols recorded in ship-tracking data going back to January 2025, according to Bloomberg’s Sept. 7 report carried by The Japan Times. The deployments began shortly after Japan and the Philippines announced plans to negotiate a maritime boundary in the region, a move Beijing opposed.
The patrols have covered about 27,100 square nautical miles — more than twice Taiwan’s land area — with Chinese vessels approaching to within about 30 nautical miles of Taiwan’s east coast while remaining outside waters claimed by Taipei. Ryan Martinson of the U.S. Naval War College’s China Maritime Studies Institute said Beijing was using the Japan-Philippines announcement “as a pretext for greatly expanding its presence in these waters.”
The activity has implications beyond Taiwan. MarineTraffic data cited by Bloomberg showed ships carrying oil, gas, iron ore and agricultural products made 527 transits east of Taiwan in June, compared with 420 through the normally busier Taiwan Strait. The Pacific side also provides access to major Taiwanese ports and military facilities and contains deep water suited to submarine operations and underwater surveillance.
“If the Taiwan Strait is the front door, then the eastern waters are often treated as the back door,” Florida International University lecturer Jing Ge told Bloomberg. Beijing, she said, is signaling that the “back door” is no longer uncontested.
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The U.S.-China Economic and Security Review Commission warned in July that Beijing’s new “routine” patrols appear designed to establish a persistent coast guard presence while avoiding the appearance of military escalation. The commission said such a presence could also help China prepare for a future blockade of Taiwan.
Taiwan warns maritime data is becoming a security issue
Taiwanese officials say the expanding Chinese presence illustrates why maritime surveillance and independent oceanographic data have become national-security priorities.
At Taiwan’s 2026 Ocean Technology Industry Forum on Sept. 7, Ocean Affairs Council Minister Kuan Bi-ling said China had announced seabed geological surveys east of Taiwan while its coast guard continued what Beijing calls law-enforcement patrols.
According to the Taiwan Ocean Affairs Council’s official account of the forum, Kuan warned that marine surveys and maritime data are not merely scientific issues when they can be used to establish jurisdictional claims, construct legal arguments and gradually alter conditions at sea.
“Taiwan and its democratic partners must possess their own maritime knowledge” and independent technology, Kuan said. She called for greater use of coastal radar, satellite monitoring, vessel-identification systems, unmanned surface and underwater vehicles and seabed sensors.
Kuan also said Taiwan should use artificial intelligence to identify unusual maritime activity, assess risks and establish early-warning thresholds. Taiwan’s National Security Council Deputy Secretary-General Li Wen told the same forum that Beijing was using a “salami-slicing” strategy involving naval vessels, coast guard ships, research vessels, maritime militia and other ships to gradually change the regional status quo.
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