The Nomenkan incident was a battle between Japan and the Soviet Union in the Far East at the beginning of World War II.

The war broke out in Nomenham on the Manchu-Mongolian border in 1939. The armies of Japan and the Soviet Union fought on behalf of "Puppet Manchukuo" and "Mongolia" (the Soviet-Mongolian coalition led by Marshal zhukov of the Soviet Union and Marshal Joe Balsan of China), but Japan and the Soviet Union did not formally declare war on each other. The war ended in a fiasco of the Japanese Kwantung Army. Japan and the Soviet Union maintained peace in the Second World War until August 6th, 1945, when the US military dropped an atomic bomb on Hiroshima, Japan, and the Soviet Union declared war on Japan on August 8th to attack the August storm of the puppet Manchukuo.

The battle of Nomonhan was caused by the ownership of the triangle area between Japanese invaders and Mongolian troops in the west of Nomonhan until the Haraha River. The battle ended in a fiasco of the Japanese Kwantung Army.