 The Soviet Union and Japan remained neutral towards each other for most of the war per agreement in the Soviet–Japanese Neutrality Pact.In the weeks before a declaration of war, Japan was actively lobbying The Soviet Union to appeal to the western allies in hopes of achieving more favorable surrender conditions.The Soviet Union ended the Soviet-Japanese Neutrality Pact by invading Manchukuo on August 8, 1945, days before the ultimate Japanese capitulation, and the end of World War II.