 Over 500,000 Japanese prisoners of war were sent to work in Soviet labor camps in Siberia, Russian Far East and Mongolia.They were largely repatriated, in stages, over the next five years, though some continued to be held well into the 1950s.After the surrender of Japan, the Soviet Red Army discovered secret installations for experimenting with and producing chemical weapons and biological weapons of mass destruction centered around secret Army Unit 731 and its subsidiaries.