In the Soviet invasion of Manchuria it led the attack into Japanese-occupied Manchuria. Although the Kwantung Army of the Imperial Japanese Army had more than 1 million soldiers, the Japanese defenders were overwhelmed by the offensive. Allied forces of Mongolia and Chiang Kai-shek's Nationalist China aided the Soviet operation. On August 19, the Far East Front continued its routing of the Kwantung Army by capturing Harbin and Mukden. By August 21, the Red Army had captured almost all of Manchuria, and the final surrender of the Kwantung Army took place.