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In the late 1930s, Stalin faced the possibility of a two-front war, with the Germans invading from the west and the Japanese from the east. In 1939 he postponed the threat in the west by his pact with Hitler, and made the threat from Japan less likely by the Soviet victory at Nomanham.

Stalin was in a position of near total control of Soviet policy. Historically he decided to shore up the Soviet position in the west in late 1939 and early 1940 by seizing the Baltic states, parts of Romania, and part (original intent was all) of Finland. What if he had decided to deal decisively with Japan while Germany was tied up fighting the western Allies. He, like almost everybody else except the Germans, was expecting a repeat of World War I on the western front, with the short front lines and massive amounts of firepower on both sides leading to a prolonged war of attrition. Why not take advantage of the Allied and Germany preoccupation with that war to settle things once and for all with Japan?

Seems more logical than a lot of his decisions. One problem though: While Stalin probably didn't realize the extent to which his purges had gutted the Soviet Army, if he went ahead with his attack on Finland he would quickly figure out how badly disorganized his army was. The only way this would be feasible is if the decision to attack Japan precluded an attack on Finland for some reason--maybe logistics reasons or not wanting to risk hacking off the Germans before they were fully involved in their attack on France.

In any case, the Soviets quietly build up in the Far East, bringing in their latest tanks and the units they regard as elite. In the weird political/military environment the Soviets were operating in during this time period that could mean anything from truly elite forces to forces led by Stalin's favorite toady. On May 10, 1940, the Germans launch their war in the West. A day or two later, Stalin launches a surprise attack against the Japanese in Manchuria, presumably spearheaded by a handful of KV1s, though without the Winter War the Soviets might conceivably have gone with one of the two-turreted monstrosities that they tested alongside it in the Winter War.

So how does the invasion go? Would the Soviets be able to manage a surprise 'bolt from the blue? What would happen next?
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