Senkaku Islands dispute

The Senkaku Islands dispute, or Diaoyu Islands dispute, is a territorial dispute over a group of uninhabited islands known as the Senkaku Islands in Japan, the Diaoyu Islands in China, and Tiaoyutai Islands in Taiwan. Japan controlled the islands from 1895 until the end of World War II in 1945, after which the United States controlled the islands, which it administered as part of the Ryukyu Islands. In 1972, the United States transferred the islands to Japan. The islands are administered as part of the Okinawa Prefecture.

The islands are positioned close to key shipping lanes and rich fishing grounds, and there may be oil reserves in the area. Japan argues that it surveyed the islands in the late 19th century and found them to be terra nullius (Latin: land belonging to no one); subsequently, China acquiesced to Japanese sovereignty until the 1970s. According to Lee Seokwoo, China started taking up the question of sovereignty over the islands in the latter half of 1970 when evidence relating to the existence of oil reserves surfaced. Taiwan also claims the islands. The PRC and the ROC argue that documentary evidence prior to the First Sino-Japanese War indicates Chinese possession and that the territory is accordingly a Japanese seizure that should be returned as the rest of Imperial Japan's conquests were returned in 1945.

In September 2012, the Japanese government purchased three of the disputed islands from their private owner, prompting large-scale protests in China and Taiwan. Although Japan viewed its move as an attempt to defeat Tokyo governor Shintaro Ishihara's more provocative attempt to buy the islands to develop infrastructure on them, the Chinese side viewed the purchase as an effort by Japan to bring the islands under Japanese sovereignty. On 23 November 2013, the PRC set up the East China Sea Air Defense Identification Zone which includes the Senkaku Islands, and announced that it would require all aircraft entering the zone to file a flight plan and submit radio frequency or transponder information.

The islands are included within the 1960 Treaty of Mutual Cooperation and Security between the United States and Japan, meaning that a defense of the islands by Japan would require the United States to come to Japan's aid.