The League of Nations deemed the attack illegal and expelled the Soviet Union from the League on 14 December 1939.
The Red Army faced a disastrously underestimated opponent, suffering a series of embarrassing defeats.
However in 1940 the Soviets reorganized their forces and mauled the enemy in a final great offensive. Mannerheim, the Finnish commander, then advised his government to negotiate peace on Soviet terms. Recognizing that they had lost the war, the Finns wisely chose to settle early with the Soviets, while there was still potential for a relatively lenient peace treaty. In the end, the Finns retained their independence, but ceded huge tracts of territory, and resources, to the victorious Soviets.