China has expanded its maritime operations around Taiwan to include non-naval vessels. In doing so, its efforts to assert authority over the island have stepped up significantly.

By normalising its claim of jurisdiction to the east, China is shortening the step it would take in imposing a quarantine, an attempt at controlling what ships go to or from Taiwan. Analysts think a quarantine could be the opening move in an attempt at seizing control of the island.

Previously, Chinese government vessels operating east of Taiwan were mainly warships engaged in military exercises. But in June, for the first time, China sent vessels of its Transport Ministry, which is responsible for securing sea lanes, to seas east of Taiwan in a ‘special maritime traffic law-enforcement operation.’ The China Coast Guard and marine survey vessels under China’s Ministry of Natural Resources also took part.  Then, on 4 July the coast guard said a new patrol group would take over from the first one and continue with routine ‘law-enforcement patrols’ in the area. This implies that China’s non-naval presence in Taiwan’s eastern seas will be continuous.

The Global Times, a Chinese Communist Party media outlet, said China’s control of the waters east of Taiwan had entered a ‘new phase’. A spokeswoman for Beijing’s Taiwan Affairs Office said on 2 July the patrols were a ‘lawful exercise of jurisdiction, a just act to safeguard national territorial sovereignty and maritime rights and interests.’

The June patrol east of Taiwan involved the coast guard harassing commercial ships in the eastern seas by demanding to know their ports of departure and destinations. In June, China’s Ministry of Natural Resources also conducted marine environment surveys and Ministry of Transport vessels mapped Taiwan’s eastern seabed, where Taiwanese and Japanese undersea cables are believed to be laid and where the Pacific Ocean’s continental shelf drops rapidly. These features make the area crucial for submarine warfare.

China Global Television Network said China had previously conducted individual scientific projects in this area but, in a new twist, this marine environment survey mission formed ‘part of a regular survey program, indicating a move towards more systematic and long-term monitoring.’

Note: ‘regular’ and ‘long-term’.

Su Tzu-yun, an analyst with Taiwan’s government-funded Institute for National Defense and Security Research, dubs these latest Chinese tactics ‘dark grey-zone operations’.

‘To the northeast lies the Ryukyu Trench, while farther south the seabed drops into deeper waters, creating … a paradise for submarines,’ Su said. China’s

‘main objective is likely to collect data on the seabed topography, ocean currents, salinity, temperature and other hydrographic conditions, all of which are essential for future submarine operations and anti-submarine warfare planning.’

He added that he thought Beijing had assessed that its seven large-scale military exercises held since 2022 had had limited effect and was adjusting its approach. Apart from their military value, Chinese exercises near the island are widely seen as aimed at persuading Taiwan to obey Beijing.

The first Chinese patrol provoked a rare joint statement on 24 June from the British, German and French diplomatic missions to Taiwan (embassies in all but name) that denounced the novel activity in the island’s eastern waters.

‘These actions threaten regional stability and the freedom of navigation and safety of international shipping,’ they said.

The de facto US embassy, the American Institute in Taiwan, told media that the United States rejected any claim by China of authority to interfere with navigation and overflight, the freedom to lay undersea cables, and other lawful uses of the sea in the area.

In China, the Taiwan Affairs Office spokesperson said Beijing had sent the patrols in response to talks between Japan and the Philippines that began in May to set boundaries between their exclusive economic zones. Tokyo and Manila were deliberately bypassing China without permission, she said. Because China declares Taiwan to be its own territory, it also claims an exclusive economic zone to the east of the island.

Huang Kwei-bo, a professor at National Chengchi University’s department of diplomacy, said Beijing was extending its assertion of jurisdiction to the eastern waters because it wanted to have a say in the boundary settlement.

On 4 July, Taiwan’s Mainland Affairs Council lashed out at the news of the second patrol, saying the CCP had no sovereignty or authority in waters east of Taiwan.

‘“Illegal acts” remain illegal no matter how many times they are committed and will not be recognized internationally,’ the council said in a statement. It added that the Taiwanese coast guard would respond with concrete action, though it didn’t specify what this would be. This raises fears about accidents or collisions that could escalate cross-strait tensions.

A permanent presence from Chinese law enforcement vessels in Taiwan’s eastern seas will also make it much easier for China to upgrade these patrols into a quarantine encircling Taiwan. ‘It functions as a rehearsal for a potential maritime blockade of Taiwan by gradually normalising Chinese presence and administrative control in the surrounding waters,’ Su said.