Upon the intervention of the Soviet Union against Japan in World War II in 1945, USSR forces invaded the Japanese client state of Manchukuo. Mao Zedong in April and May 1945 had planned to mobilize 150,000 to 250,000 soldiers from across China to work with forces of the Soviet Union in capturing Manchuria.[3] After the end of the war, the communists controlled one-third of the territory of China.