Winter War

For 105 days in the winter of 1939–40, Finland held off an invasion by the Soviet Union, a neighbour with far more tanks, aircraft and soldiers. The fighting began on 30 November 1939 and ended in March 1940 with a peace that cost Finland about nine per cent of its territory, but the country kept its independence, and the Red Army's poor showing shaped calculations in Berlin and in Western capitals.

Finland had broken away from the collapsing Russian Empire in December 1917, and the 1920 Treaty of Tartu fixed a border that ran only about 32 kilometres from Leningrad. Joseph Stalin and his government saw this as a security threat. The Molotov–Ribbentrop Pact of August 1939 placed Finland in the Soviet sphere of influence, and from October Soviet negotiators pressed the Finns to move the frontier on the Karelian Isthmus westwards and to hand over or lease islands and bases, offering land in East Karelia in return. Finland refused the main demands.

On 26 November 1939 a Soviet border post near the village of Mainila was shelled. Moscow blamed Finland, but historians from both countries later concluded that the shots were fired from the Soviet side as a pretext. Four days later, without a declaration of war, Soviet forces crossed the border and bombed Helsinki. A puppet "Finnish Democratic Republic" under the communist Otto Wille Kuusinen was set up in occupied territory. The League of Nations expelled the Soviet Union on 14 December.

Marshal Carl Gustaf Emil Mannerheim took command of the Finnish forces, which held a fortified belt on the Karelian Isthmus known as the Mannerheim Line. In temperatures that fell to around minus 43 °C, Finnish ski troops used the forests to cut road-bound Soviet columns into isolated pockets. At Suomussalmi and on the Raate road, a Soviet force of about 14,000 men was almost destroyed. The Finns improvised anti-tank weapons, including the petrol bomb they named the Molotov cocktail.

In January 1940 Moscow dropped the puppet government and signalled it would deal with the government in Helsinki. Meanwhile the Red Army reorganised. By 11 February it had about 460,000 men and some 3,000 tanks on the Karelian Isthmus, facing roughly 150,000 Finns. A massive artillery-backed offensive broke through at Summa, and by early March Soviet troops were in the outskirts of Viipuri. With ammunition running out and no Western help arriving in time, Finland accepted Soviet terms.

The treaty was signed in Moscow on 12 March 1940, and the guns fell silent the next day. Finland gave up the Karelian Isthmus, including Viipuri, most of Ladoga Karelia, part of Salla, the Rybachy Peninsula and several islands, and leased the Hanko peninsula to the Soviet Union for 30 years. These losses went beyond the Soviet demands made before the war. Between 422,000 and 450,000 Karelians, about 12 per cent of the population, left their homes.

According to revised figures published by Finnish historians in 2005, 25,904 Finns died or went missing and 43,557 were wounded. Soviet dead and missing are estimated at between about 127,000 and 168,000. The war encouraged Adolf Hitler to believe that the Red Army was weak, and after 15 months of uneasy peace, as Germany launched Operation Barbarossa in June 1941, fighting between Finland and the Soviet Union resumed in what Finns call the Continuation War.

Our 1938 map shows Finland with its pre-war eastern border, and our 1945 map shows Karelia and the land around Lake Ladoga inside the Soviet Union.