East China Sea dispute

The East China Sea dispute centers on a cluster of small uninhabited islands administered by Japan as the Senkaku Islands, claimed by the People's Republic of China as the Diaoyu Islands, and by Taiwan as the Diaoyutai Islands. The islands sit roughly northeast of Taiwan and southwest of Okinawa, in waters believed to contain hydrocarbon reserves and rich fisheries.

Japan formally incorporated the islands in 1895, arguing they were terra nullius. After World War II they were administered by the United States and returned to Japan under the 1971 Okinawa Reversion Agreement, which took effect in 1972. China and Taiwan began asserting claims publicly around 1971, partly after a 1968 UN ECAFE survey suggested possible oil and gas deposits beneath the seabed.

The dispute also involves overlapping Exclusive Economic Zone (EEZ) and continental shelf claims under the UN Convention on the Law of the Sea (UNCLOS). Japan favors a median-line approach; China invokes natural prolongation of its continental shelf toward the Okinawa Trough. A 2008 bilateral agreement on joint development of gas fields near the median line was never implemented.

Tensions escalated sharply in September 2012, when the Japanese government purchased three of the islands from a private owner, triggering large anti-Japanese protests in Chinese cities and a surge in Chinese maritime and air incursions near the islands. In November 2013, China declared an Air Defense Identification Zone (ADIZ) covering the area, which Japan, the United States, and South Korea rejected.

The dispute is strategically significant because the United States has repeatedly affirmed that Article 5 of the 1960 U.S.-Japan Treaty of Mutual Cooperation and Security applies to the Senkakus, meaning an armed attack there could trigger U.S. defense obligations. Coast guard standoffs, fishing-vessel incidents, and scrambles by Japanese F-15s against Chinese aircraft remain routine, making the area one of East Asia's most persistent flashpoints.