On September 29 the China Coast Guard announced that a task group led by the cutter Zhujiajian had carried out “routine law-enforcement patrols” in the waters east of Taiwan. The announcement added a detail that matters more than the patrol itself. The group, Beijing said, had been “strengthening control” over those waters since the start of September.

Taiwan’s coast guard had been watching. Its cutter Lanyu shadowed two Chinese ships, the Zhujiajian (hull 2503) and the Chongming (1401), and placed them roughly 97 nautical miles northeast of Green Island and 146 nautical miles east of Lanyu. Far from the Strait. Far from Fujian. On the Pacific side of the island, where Taiwan’s east-coast ports and air bases face open water.

Kinmen Island sits approximately 3.5 kilometers from the Chinese city of Xiamen. On a clear day, residents of Kinmen can see the skyline of a Chinese city of five million people across a strip of water narrower than the distance between Manhattan and Staten Island. Taiwan has administered Kinmen since 1949, when Nationalist forces successfully repelled a PLA amphibious assault that, if successful, might have changed the entire trajectory of the civil war’s outcome. The island has been shelled, blockaded, and fought over. It is still Taiwanese. Its continued existence as a piece of Taiwanese territory three kilometers from the Chinese mainland is one of the more remarkable geopolitical facts of the twentieth and twenty-first centuries.