The Senkaku Islands — known as the Diaoyu Islands in China — are eight uninhabited islands and rocks administered by Japan in the East China Sea, approximately 170 kilometers northeast of Taiwan and 330 kilometers west of Okinawa. Japan claims sovereignty. China claims sovereignty. Taiwan also claims sovereignty, though Taiwanese governments have generally handled the claim with less assertiveness than Beijing. The islands have no permanent population and no inherent economic value beyond the fisheries and potential hydrocarbon resources in the surrounding waters. Their strategic value lies entirely in their position: they sit at the junction of Japan’s Ryukyu chain and Taiwan’s northern approaches, and whoever controls them controls observation and potentially military positions that are relevant to both the East China Sea competition and the Taiwan Strait contingency.

The Center for Strategic and International Studies published a major wargame analysis of the Taiwan Strait in January 2023. It ran 24 iterations of a Chinese invasion scenario, varying assumptions about Chinese military capability, American intervention, Japanese participation, and Taiwanese defense posture. The headline finding — that the United States and its allies could likely defeat a Chinese invasion but at very high cost — made international news. The details of the analysis were more nuanced and more alarming than the headline suggested. Understanding what the wargames actually show, and what they cannot show, is prerequisite to understanding the current state of Taiwan contingency planning.