The Battle of Lake Khasan was an attempted military incursion of the Japanese 19th Division into the territory claimed by the Soviet Union. This incursion was founded in the belief of the Japanese that the Soviet Union misinterpreted the demarcation of the boundary based on the Treaty of Peking between Imperial Russia and Manchu China (and subsequent supplementary agreements on demarcation), and furthermore, that the demarcation markers were tampered with.

The following year, Nomonhan Incident (Battle of Khalkhin Gol) occurred on 11 May 1939, when a Mongolian cavalry unit of some 70 to 90 men entered the disputed area in search of grazing for their horses, and encountered Manchukuoan cavalry who drove them out of the disputed territory. Two days later the Mongolian force returned and the Manchukoans were unable to evict them.

The Japanese IJA 23rd Division and other units of the Kwantung Army then became involved. Joseph Stalin ordered STAVKA, the Red Army's high command, to develop a plan for a counterstrike against the Japanese. Georgy Zhukov led a devastating offensive employing encircling tactics making skillful use of their superior artillery, armor and air forces in late August that nearly annihilated the 23rd Division and decimated the IJA 7th Division. On September 15 an armistice was arranged. Nearly two years later, on April 13, 1941, the parties signed a Neutrality Pact, in which the Soviet Union pledged to respect the territorial integrity and inviolability of Manchukuo, while Japan agreed similarly for the Mongolian People's Republic..

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