The Soviets fought Japan in two major border incidents throughout the 1937 - 1939 period in China and Mongolia. Included in these were:

Changkufeng / Lake Kasan 1938. Both sides took several thousand casualities. The Japanese were forced to withdraw their troops from this area, at least temporarily.

Nomohan / Khalkhin Gol April 1939. Again, both sides took heavy casualities. But, the Japanese 23rd Infantry division was destroyed in the fighting (just over 70% casualities). The Japanese Army Air Force also took heavy losses. These were serious e