On August 8, 1945, after refusing to mediate a Japanese surrender with the United States and its allies, the USSR declared war on Japan.

On August 9, 1945, Russian troops invaded the Japanese puppet state of Manchukuo in Operation August Storm.

On August 14, 1945 a Soviet armored division and some Chinese troops massacred ~1500 Japanese civilians near Gegenmiao Manchuria. Japanese refugees (mostly women and children) were reportedly shot, run over by tanks or trucks or bayoneted after they had raised a white flag in surrender.

Soviet and Mongolian troops soon ended Japanese control of Manchukuo, Mengjiang (inner Mongolia),  South Sakhalin Island (Karafuto), and the Chishima (Kuril) Islands and northern Korea.