The Potsdam Declaration named four principal Japanese home islands when defining Japan's postwar sovereignty.
The islands listed were Honshu, Hokkaido, Kyushu, and Shikoku. The declaration also allowed for sovereignty over additional minor islands designated by the Allies. This language established the territorial framework for reducing Japan's wartime empire after surrender.
The provision reflected broader Allied decisions made during the war, including the Cairo Declaration. Japan was expected to relinquish territories acquired through conquest, including Korea and Taiwan, while its future sovereignty would be concentrated on the home islands and selected smaller islands.
The phrase “four home islands” can cause confusion because Japan is an island country with thousands of islands. In the surrender context, the number refers to the four principal islands named in the declaration, not to every island that would ultimately remain under Japanese administration. The four names were Honshu, Hokkaido, Kyushu, and Shikoku.