USSR invades Finland with 21 divisions, violating three non-aggression pacts.
At 6.50 AM, artillery barrage starts on the Karelian Isthmus. At 8 AM, Soviet 7th Army advances across the entire Isthmus into mine fields pre-ranged by Finnish machine guns and artillery. 9 Soviet infantry divisions plus tanks (250,000 men) are held by Finnish covering forces (21,000 men) in front of the main defensive line (Mannerheim Line). Soviet planes bomb Helsinki.
Initially, Soviet attacks along the 800-mile border from Ladoga to the Arctic Sea meet little resistance. Eighth Army advances north of Lake Ladoga. Ninth Army strikes into central Finland for the Gulf of Bothnia to cut Finland in half. Fourteenth Army aims to capture the Arctic port of Petsamo.