The Dioayutai Islands refers to an archipelago located northeast of Taiwan that is claimed by Taiwan, Mainland China, and Japan. The islands are called the Senkaku Islands in Japanese.
While the island chain is uninhabited, it is rich in fishery and energy resources, including an underwater oil field. The islands have long been a sore spot in Sino-Japanese relations. Today, Japan claims the islands are part of Okinawa Prefecture, while both Mainland China and Taiwan claim the islands as part of northeastern Taiwan's Yilan County.
The five islands and three barren rocks became important in 1879, when Imperial Japan annexed the Ryukyu Kingdom and renamed it to Okinawa. After that expansion, the Diaoyutai Islands became the only buffer between Japan's southernmost point and Taiwan, which was the easternmost holding of China's Qing dynasty.
Controversy over the island chain's ownership began in 1895, when Japan incorporated the islands at the outbreak of the First Sino-Japanese War. Months later, the Qing government gave control of Taiwan and its surrounding islets to Japan as part of the Treaty of Shimonoseki.
The 1895 treaty was superseded by the Treaty of San Francisco that Japan signed with the Allied Powers in 1951 after Japan lost the Second World War. In the new treaty, Japan relinquished the control of Taiwan and its surrounding islets.
However, there are disputes over whether the Diaoyutais are Taiwan’s surrounding islets. In 1972, when the United States ended its occupation of Okinawa, control of the Diaoyutai Islands was also handed over to Japan. To this day, Japan remains in effective control of the area.
Both Taipei and Beijing asserted sovereignty over the islands. Both governments say that the islands have been historically included in maps of Taiwan for centuries, and they never granted Japan permission to occupy the area.