High Quality Content by WIKIPEDIA articles! Unit 516 was a top secret Japanese chemical weapons facility, operated by the Kempeitai, in Qiqihar, Manchukuo. The name Unit 516 was a code name (Ts sh g ) of the Unit.An estimated 700,000 (Japanese estimation) to 2,000,000 (Chinese estimation) Japanese-produced chemical weapons were buried in China. Until 1995, Japan had refused to acknowledge that it dumped chemical weapons in the Yen River in Manchuria, leaving huge amounts behind.