Nomonhan Incident; Battle of Khalkhin Gol
Refers to the 1939 Soviet–Japanese border conflict. In Japanese, ノモンハン事件 is the common name; in English both 'Nomonhan Incident' and 'Battle of Khalkhin Gol' are used.
The Nomonhan Incident occurred in 1939 on the border between Manchukuo and Mongolia.