The Winter War (Finnish: talvisota, Swedish: vinterkriget,
Russian: Зимняя война, tr. Zimnyaya voyna) was a military
conflict between the Soviet Union and Finland. The conflict
began with a Soviet offensive on 30 November 1939—two months
after the start of World War II and the Soviet invasion of
Poland—ending on 13 March 1940 with the Moscow Peace Treaty. The
League of Nations deemed the attack illegal and expelled the
Soviet Union from the League on 14 December 1939. The Red Army
aimed to recover the Grand Duchy of Finland territory lost
during the Russian Civil War in 1917, during which Finland had
declared independence from Russia. The Soviet Union demanded the
territories for security reasons, primarily to protect
Leningrad, which was 40 km from the Finnish border. The Soviets
possessed more than three times as many soldiers as the Finns,
thirty times as many aircraft, and a hundred times as many
tanks. The Red Army, however, had been crippled by Soviet leader
Joseph Stalin's Great Purge of 1937, reducing