ノモンハン事件
The Battles of Khalkhin Gol began on 11 May 1939. A Mongolian cavalry unit of some 70–90 men had entered the disputed area in search of grazing for their horses. On that day, Manchukuoan cavalry attacked the Mongolians and drove them back across the Khalkhin Gol. On 13 May, the Mongolian force returned in greater numbers and the Manchukoans were unable to dislodge them.