Before Imperial Japan attacked the United States at Pearl Harbor it had already attacked the Soviet Union: true or false?

This action is known as the Battles of Khalkhin Gol and took place in 1939 in an attempt by Japan to expand its borders northwestward through Mongolia; it started out as fairly minor skirmishes and then led to a serious assault by Japan on Soviet troops; Japan lost.

While this engagement is little-known in the West, it is nevertheless surprisingly important. The victor of Khalkhin Gol -- Georgy Zhukov - went on to play a vital role in the war against Germany (he used essentially the same strategy at Stalingrad). It played an important part in subsequent Japanese conduct in World War II. The battle earned the Kwantung Army the displeasure of officials in Tokyo, not so much due to its defeat, but because it was initiated and escalated without direct authorization from the Japanese government. This defeat, together with the signing of the Nazi-Soviet non-aggression pact (which deprived the Army of the basis of its war policy against the USSR), moved the Imperial General Staff in Tokyo away from the policy of the North Strike Group favoured by the Army, which wanted to seize Siberia for its resources as far as Lake Baikal.