Reformed at Birobidzhan, Soviet Union, from the 2nd Red Banner Army in June 1940. It formed in July 1940 as part of the Far Eastern Front. Until August 1945 the army defended the Far Eastern borders of the USSR. On August 5 it was incorporated into the newly created 2nd Far Eastern Front. On August 9, during the Soviet–Japanese War, the 15th Army, consisting of shock troops, participated in the Sungari operation. Its advance units entered Harbin on August 20. Through the end of August the 15th Army destroyed the scattered pieces of the Japanese Kwantung Army. Conducted border operations through mid-1945. Participated in the Soviet invasion of Manchuria and the crossing of the Amur River in August 1945.