On Monday, China reacted angrily to Britain’s decision to send a Royal Navy cruiser sailing across the strategically important Taiwan Strait, claiming that the action “harbored evil intentions.” China claims democratically-ruled Taiwan as its own territory, and in recent years has stepped up pressure on the island to recognize Beijing as its capital.

The HMS Richmond, a frigate deployed as part of a UK aircraft carrier strike group, sailed through the Taiwan Strait on Monday, putting Beijing’s claim to the strategic waterway to the test.

“This kind of behavior harbors evil intentions and damages peace and stability in the Taiwan Strait,” the Chinese army’s Eastern Theater Command said.

In response to the transit, the Chinese army sent air and naval forces to shadow the HMS Richmond. It was the second time a British warship had passed across the tight canal dividing Taiwan and mainland China. The British military survey ship HMS Enterprise first passed through the straight in 2019.

Regular “freedom of navigation” drills by US warships have repeatedly sparked angry responses and threats of retaliation from Beijing. Most nations, including the United States, see such areas as international seas that should be available to all ships. In recent years, Canadian, French, and Australian warships have all sailed across the Taiwan Strait, provoking Chinese complaints.

Chiu Kuo-cheng, Taiwan’s defense minister, confirmed to reporters that a foreign warship had passed through the strait, but did not specify whose country it belonged to.

Taiwan’s 23 million inhabitants are believed to be on the verge of being invaded by authoritarian China, which has threatened to take the island by force if necessary.

Since the election of President Tsai Ing-wen in 2016, Beijing has increased military, diplomatic, and economic pressure on Taiwan. Tsai Ing-wen sees Taiwan as a fully independent and democratic nation.