Sphère de coprospérité de la grande Asie orientale
As Japan was extending its influence over East Asia and the Pacific through the establishment of a Greater East Asia Co-Prosperity Sphere, the Imperial Japanese Army as part of its offensive contingency plans to invade the Soviet Union if it either became involved in the Pacific War or collapsed due to the ongoing German invasion, proposed the annexation of the remaining northern half of Sakhalin to Japan.