The Winter War was a military conflict between the Soviet Union and Finland. It began with a Soviet offensive on 30 November 1939â€”two months after the start of World War II and the Soviet invasion of Polandâ€”and ended 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 Soviets had 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 the army's morale and efficiency shortly before the outbreak of the fighting. With more than 30,000 of its army officers executed or imprisoned, including most of those of the highest ranks, the Red Army in 1939 had many inexperienced senior and mid-level officers. Because of these factors, and high morale in the Finnish forces, Finland was able to resist the Soviet invasion for far longer than the Soviets expected.
Hostilities ceased in March 1940 with the signing of the Moscow Peace Treaty. Finland ceded 11% of its pre-war territory and 30% of its economic assets to the Soviet Union. Soviet losses were heavy, and the country's international reputation suffered. Soviet forces did not accomplish their objective of the total conquest of Finland, but did gain substantial territory along Lake Ladoga, providing a buffer for Leningrad, and territory in Northern Finland. The Finns, however, retained their sovereignty and enhanced their international reputation.
The peace treaty thwarted the Franco-British plan to send troops to Finland through northern Scandinavia. One of the operation's major goals had been to take control of northern Sweden's iron ore and cut its deliveries to Germany; for this reason, it was also a major reason for the launching of Operation WeserÃ¼bung.
In August 1939, the Soviet Union and Nazi Germany signed the Molotovâ€“Ribbentrop Pact, in which Eastern European countries were divided into spheres of interest; Finland belonged to the Soviet sphere of interest. In October 1939, Stalin gained control of the Baltic states and turned his sights on Finland, confident that control could be gained without great effort. The Soviet Union demanded territories on the Karelian Isthmus, the islands of the Gulf of Finland and a military base near the Finnish capital Helsinki, similar to the demands presented in the previous years. The Finns again refused, and the Red Army attacked on 30 November 1939. Simultaneously, Stalin set up a puppet government for the Finnish Democratic Republic, headed by the Finnish communist Otto Wille Kuusinen.