Prelude

http://historyofrussia.org/khalkhin-gol-battle-nomonhan/

In August 1939, just weeks before Hitler and Stalin invaded Poland, the Soviet Union and Japan fought a massive tank battle on the Mongolian border – the largest the world had ever seen.

Under the then unknown Georgy Zhukov, the Soviets won a crushing victory at the batte of Khalkhin-Gol (known in Japan as the Nomonhan Incident). Defeat persuaded the Japanese to expand into the Pacific, where they saw the United States as a weaker opponent than the Soviet Union. If the Japanese had not lost at Khalkhin Gol, they may never have attacked Pearl Harbor.

The Japanese decision to expand southwards also meant that the Soviet Eastern flank was secured for the duration of the war. Instead of having to fight on two fronts, the Soviets could mass their troops – under the newly promoted General Zhukov – against the threat of Nazi Germany in the West.

In terms of its strategic impact, the battle of Khalkhin Gol was one of the most decisive battles of the Second World War, but no-one has ever heard of it. Why?

Rising Tensions
It was perhaps not all that surprising that the Soviet Union and Japan, two expansionist powers who just happened to be close neighbours, butted heads in the Mongolian borderlands.

Tensions between the two had been high for decades, and had erupted into open conflict on a number of occasions. Japan had clearly had an edge over Russiaduring the early part of the 20th century – it had decisively defeated Tsarist Russia in the Russo-Japanese war of 1905 (a conflict most memorable, perhaps, for the Russian Navy’s folly of sailing its entire Baltic fleet around the globe only to be promptly sunk by the Japanese Navy within days of its arrival), and had occupied Vladivostock for several years during the Russian civil war.

But, by the 1930s, the Soviet Union under Stalin was a resurgent power, and had become a major regional rival to the Japanese. The Japanese High Command were particularly concerned about the threat Soviet submarines posed to Japanese shipping, and the ease with which Soviet bombers, operating out of Vladivostok, would be able to reach Tokyo.