During most of the Second Sino-Japanese War and due to the Soviet–Japanese Neutrality Pact, Inner Mongolia was largely a backwater region, and the Mongolia Garrison Army, with its antiquated horse cavalry functioned largely to assist and train the Mengjiang National Army and Mongolian Cavalry Corps. It was thus unprepared for the massive Soviet Red Army armored assault at the end of World War II. The Mongolia Garrison Army was officially disbanded on July 27, 1946. Many of its survivors became Japanese prisoners of war in the Soviet Union.