The Senkaku Overlap: How Japan's Island Dispute Entangles With Taiwan's Security
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 American position on the Senkakus — that they fall under the US-Japan Security Treaty’s Article 5 commitment, which obligates the United States to defend Japanese-administered territory — was restated in the Obama administration and has been maintained by subsequent administrations. The commitment is designed to deter Chinese seizure of the islands by making clear that such a seizure would constitute an attack on Japan and trigger American involvement. The deterrent has been at least partially effective: China has not attempted to seize the islands, though its coast guard and maritime militia vessels have operated in the waters around them with increasing frequency and have approached them closely enough to require Japanese coast guard response.
The relationship between the Senkaku dispute and a Taiwan contingency operates through several channels. First, PLA operations in a Taiwan scenario would occur in the general vicinity of the Senkakus, and the ambiguity about whether specific PLA actions constitute threats to Senkaku-adjacent Japanese territory would create political and military complications for Japanese decision-making. A Japanese government trying to decide whether to authorize American use of Japanese bases for Taiwan contingency operations while simultaneously managing a Chinese military presence near the Senkakus faces a more complex decision than a government dealing with either issue in isolation.
Second, the Senkakus could serve as a deliberate Chinese pressure point during a Taiwan crisis — not as a primary objective, but as a tool for splitting Japanese attention and creating domestic political pressure on Japanese leadership. A Chinese escalation near the Senkakus that stopped short of a clear act of war — coast guard vessels that crossed into the 12-nautical-mile territorial sea, for example — would force Japan to respond in ways that consume attention, create political controversy, and complicate the decision about Taiwan.
Third, the Senkaku dispute has been an accelerant for Japanese defense investment and strategic reorientation that has ultimately strengthened the Taiwan defense posture. The persistent Chinese pressure on the Senkakus — the coast guard presence, the ADIZ established over the East China Sea in 2013, the submarine transits through Japanese territorial waters — has provided the Japanese public with a visceral demonstration of Chinese territorial assertiveness that abstract arguments about Taiwan’s democracy have not. The public that watches Chinese coast guard vessels approaching Japanese islands year after year develops a threat perception that translates into political support for defense spending and strategic reorientation that a purely theoretical Taiwan argument would not generate.
Taiwan’s own claim to the Senkakus creates an awkward triangular relationship. Taiwan and Japan are close informal partners with deep people-to-people ties, extensive economic integration, and a shared interest in preventing Chinese military coercion. They are also claimants to the same uninhabited rocks. Taiwanese governments have managed the incongruity by not pressing the claim in ways that would complicate the Taiwan-Japan relationship, while not formally relinquishing it. The claim is maintained without being prosecuted, which is a reasonable approach to a sovereignty dispute that serves nobody’s interests by being tested.
Islands that nobody lives on. A dispute that shapes the behavior of major powers. Geography’s leverage over politics does not require population to be effective.