Surrender of the Kwantung army. The Kwantung Army was stationed in Manchukuo and was one of the main Japanese fighting forces during the Second Sino-Japanese War from 1937. In August 1945, the Kwantung Army surrendered to the Soviets the day after the Surrender of Japan and was subsequently dissolved. The Kwantung Army was responsible for many of the worst Japanese war crimes during World War II, including the sponsorship of Unit 731 which performed biological warfare and human experimentation.