台湾はいつ中国に返還されましたか？
In 1942, after the United States entered the war against Japan and on the side of China, the Chinese government under the KMT renounced all treaties signed with Japan before that date and made Taiwan's return to China (as with Manchuria, ruled as the Japanese wartime puppet state of "Manchukuo") one of the wartime objectives. In the Cairo Declaration of 1943, the Allied Powers declared the return of Taiwan (including the Pescadores) to the Republic of China as one of several Allied demands. In 1945, Japan unconditionally surrendered with signing of the instrument of surrender and ended its rule in Taiwan as the territory was put under the administrative control of the Republic of China government in 1945 by the United Nations Relief and Rehabilitation Administration. In accordance with the provisions of Article 2 of San Francisco Peace Treaty, the Japanese formally renounced the territorial sovereignty of Taiwan and Penghu islands, and the treaty was signed in 1951 and came into force in 1952. At the date when the San Francisco Peace Treaty came into force, the political status of Taiwan and Penghu Islands was still uncertain. The Republic of China and Japan signed the Treaty of Taipei on April 28, 1952 and the treaty came into force on August 5. Writing in the "American Journal of International Law", professors Jonathan I. Charney and J. R. V. Prescott argued that "none of the post–World War II peace treaties explicitly ceded sovereignty over the covered territories to any specific state or government."
1942