From 1932 to 1945 the Empire of Japan and the Soviet Union had a series of conflicts . Japan had set its military sights on Soviet territory as a result of the '' Hokushin-ron '' doctrine , and the Japanese establishment of a puppet state in Manchuria brought the two countries into conflict . The war lasted on and off with the last battles of the 1930s ( the Battle of Lake Khasan and the Battles of Khalkhin Gol ) ending in a decisive victory for the Soviets . The conflicts stopped with the signing of the Soviet – Japanese Neutrality Pact on April 13 , 1941 . However , later , at the Yalta Conference , Stalin agreed to declare war on Japan ; and on August 5 , 1945 , the Soviet Union voided their neutrality agreement with Japan
Yalta Conference
Yalta Conference
Imperial Japanese Army