Key point: The Soviet Union was an important distraction for America's war against Japan
The Second World War was an unparalleled calamity for the Soviet Union. As many as 27 million Soviet soldiers and civilians died as a result of the conflict that started with the German invasion of Poland in September 1939 and ended with the Japanese surrender in August 1945.
Consumed by this existential struggle along its western border, the Soviet Union was a comparatively minor factor in the Pacific War until the very end. Yet Moscow’s timely intervention in the war against Japan allowed it to expand its influence along the Pacific Rim.
With the breakdown of Allied unity soon heralding the onset of the Cold War, Soviet gains in Asia also left a legacy of division and confrontation, some of which endure into the present.
By the 1930s, Stalin’s Soviet Union and Imperial Japan both viewed themselves as rising powers with ambitions to extend their territorial holdings. In addition to a strategic rivalry dating back to the 19th century, they now nursed an ideological enmity born of the Bolshevik Revolution and the ultraconservative military’s growing hold on Japanese politics. In 1935, Japan signed the Anticomintern Pact with Hitler’s Germany, laying the foundation for the creation of the Axis (Fascist Italy would join the following year).
The two militaries engaged in a series of skirmishes along the frontier between Soviet Siberia and Japanese-occupied Manchuria (Manchukuo) during the late 1930s. The largest, at Khalkin Gol in the summer of 1939, left more than 17,000 dead. Yet worried by growing tensions in Europe and Southeast Asia, both Moscow and Tokyo recognized that their respective ambitions in Manchuria were not worth the mounting costs and soon turned their attention to other theaters.
Just two days after the German Wehrmacht launched Operation Barbarossa in June 1941, Moscow and Tokyo signed a non-aggression pact. Freed from the danger of a two-front war, the Soviet Union was able to focus all its resources on resisting the German onslaught. The Red Army consequently played virtually no role in the Pacific war that was soon raging, at least until the very end.