The so-called Winter War was a military conflict between the Soviet Union (USSR) and Finland. It began with the Soviet invasion of Finland on November 30, 1939, three months after the outbreak of World War II, and ended three and a half months later with the Moscow Peace Treaty on March 13, 1940. Finland was able to fend off the Soviet attacks for more than two months and inflicted significant losses on the invaders, even as temperatures dropped to -43 °C. After reorganizing its military and devising new tactics, the Soviet forces intensified their offensive in February and overcame the Finnish defensive positions. This volume examines, among other things, the decisive military operations, support from other nations, the aftermath, and contemporary opinions on the conflict.