Soviet Entry into the War against Japan and Invasion of Manchuria

Having notified Japan in April 1945 that it would not renew the 1941 Neutrality Pact, the Soviet Union declared war on the evening of 8 August (Moscow time) and opened its offensive in the early hours of 9 August. Soviet forces under Marshal Aleksandr Vasilevsky numbered more than 1.5 million men; the Kwantung Army under Gen. Yamada Otozo had about 700,000 on paper but had been stripped of its best units and equipment.

The Kwantung Army headquarters at Hsinking (Changchun) withdrew toward Tonghua, Emperor Puyi left the capital and abdicated on 18 August, and Manchukuo ceased to exist. Fighting continued locally after Japan's surrender announcement on 15 August, with ceasefires taking effect in the following days. Soviet forces also attacked southern Sakhalin from 11 August and landed on Shumshu in the northern Kuriles on 18 August.

The invasion was one of the factors that led the Japanese government to accept the Potsdam Declaration; historians differ on its weight relative to the atomic bombings. For Japanese civilians in Manchuria, including agricultural settlers, the collapse brought flight, violence, starvation and disease. Japanese accounts commonly cite about 245,000 deaths among Japanese in Manchuria during and after the invasion, a figure that is an estimate.

According to Japan's Ministry of Health, Labour and Welfare, about 575,000 Japanese servicemen and others were taken to the Soviet Union and Mongolia for forced labour, of whom about 55,000 died. The last internees returned through Maizuru in the 1950s.