The Winter War: The Soviet Invasion of Finland

Aiming to assert political influence over neighboring Finland, the Soviet Union embarked on a military offensive on November 30, 1939. The confrontation is known as the Winter War, as the fighting took place during the winter, ending on March 13, 1940. World War II had just started, and the Soviet Union, trying to safeguard its territorial security, demanded from Finland that it give up the Karelian Isthmus. Acquiring it would provide the Soviet Union with a much-needed buffer zone against potential attacks from Germany through Finland. The Soviets projected an effortless win. The strategy, however, failed. Under the leadership of General Marshal Carl Gustaf Mannerheim, the Finns showed unprecedented resistance. But capitulation was only a matter of time. On March 12, 1940, Finland ceded around 10% of its territory to the Soviet Union. However, Finland preserved its independence.

The struggle to exert Russia’s political influence over Finland dates back to the 17th and 18th centuries when Russian Tsars frequently attempted to seize Finland as part of their expansionist policies to the east and north of the Empire. Finland remained the eastern region of the Kingdom of Sweden until the early 19th century. In 1808–1809, the Finnish War occurred between the Russian Empire and Sweden. The war resulted in Russia’s victory. Finland was seized from Sweden and transformed into an independent buffer state, the Grand Duchy of Finland. The Russian Emperor Alexander I served as the Grand Duke. Alexander I granted some degree of autonomy to Finland, maintaining the Finnish legal system, culture, religion, and traditions.

By the end of the 19th century, the Russian Empire tried to limit these special rights of the Grand Duchy of Finland, aiming to politically, militarily, and culturally assimilate Finland into the Empire, intending to ensure its unity and strength. This policy, known as the Russification Policies of Finland, was conducted during 1899–1905 and 1908–1917.

The Russian Revolution of 1905 and the related 1905 national strike in Finland had a lasting socio-political impact on the country. The former four-chamber Diet was replaced by a unicameral Parliament of Finland in 1906. Human rights became a focal point during this period, particularly women’s rights. In the same year, Finnish women were granted the right to vote, becoming the first fully eligible women voters in Europe.

The chaos resulting from the Russian Revolution in 1917 gave Finland a long-awaited opportunity to gain independence. The Bolsheviks declared a general right to self-determination “for the peoples of Russia” on November 15, 1917. The right implied that the people of the former Russian Empire were granted the right of self-determination, including secession and the ability to form a separate, independent state. The same day, the Finnish Parliament announced that it had assumed power. Just a month later, on December 6, 1917, the Finnish Senate officially declared Finnish independence. Three weeks after the announcement, Soviet Russia, later the Soviet Union, recognized the new Finnish government.

The Treaty of Tartu, signed on October 14, 1920, confirmed the Soviet-Finnish border as it was during the Grand Duchy of Finland and Imperial Russia. The territorial disputes between the two nations seemed to be settled with the signing of the Treaty of Tartu. The political tensions, however, remained.

In 1921, Finns volunteered to support the East Karelian rebellion against Russia, and the Finnish government did not interfere. In response, in 1922, a cross-border raid into Finland, the so-called Pork Mutiny, was staged. The Finnish communists crossed the border, disarming and robbing the Finnish border guards.

Another treaty, the Soviet-Finnish Non-Aggression Pact, signed in 1932, promised peaceful relations between the Soviet Union and Finland while safeguarding the latter’s independence and national security. However, international security developments and the onset of World War II rendered the pact ineffective. On August 23, 1939, the Foreign Ministers of Nazi Germany and the Soviet Union signed a non-aggression pact, also referred to as the Molotov-Ribbentrop Pact. The Pact declared Finland, Estonia, and Latvia as part of the Soviet “sphere of influence,” thus allowing the Soviet Union under Joseph Stalin’s rule to reclaim the lost territories of Tsarist Russia. In this sense, Finland was perceived as part of the traditionally Russian-dominated territory.

The international security environment during the 1930s was tense and full of uncertainty. Germany, Italy, and Japan all saw the rise of fascist dictatorships with imperialistic ambitions. Under Joseph Stalin’s leadership, the Soviet Union pursued expansionist policies, and World War II seemed inevitable. After Adolf Hitler’s forces invaded Poland from the west in September 1939, Stalin ordered the Red Army to the east and soon took control of Poland’s eastern half, bringing tensions to a peak. Stalin then focused on neighboring Finland to further enhance his influence. The motive behind Stalin’s strategic calculations was the perceived threat of Nazi Germany’s invasion through Finland. Despite Finland’s declaration of neutrality at the onset of World War II, the two nations retained a deep resentment for one another. Influenced by its history of constant struggle with Russia, Finland remained anti-Russian. Joseph Stalin was concerned about a possible Finnish-German union against the Soviets.

In addition, one of the strategic Russian cities, Leningrad, today known as St. Petersburg, was located just 32 kilometers away from the Finnish border, on the eastern periphery of the Karelian Isthmus, making the city more vulnerable to military attack. For Joseph Stalin, the whole Soviet territory should have an ideal territorial security, and the close proximity of Leningrad to the Finnish border was not aligned with this perception. To resolve the issue, Joseph Stalin demanded that the Russo-Finnish border on the Karelian Isthmus be moved to the northwest. He also requested that the Russians be permitted to station troops in several strategic areas of Finland. In exchange, Finland would receive several nonstrategic lands in eastern Karelia as well as trade and security assurances from the Soviet Union.

The Finnish government refused; if agreed, Finland would be forced to abolish its defense infrastructure on the exchanged territories. It would also become militarily vulnerable in the event of future Russian aggression, which, as history dictated, was highly probable. Finland’s determined resistance was also the result of their false assumption that Western democracies would intervene to prevent Soviet expansion.

On October 12, the representatives of the Soviet Union and Finland met in Moscow, Russia, to negotiate a mutual aid pact during World War II and also on the selling, leasing, or exchanging of disputable territories having strategic significance in the case of military actions. The Finnish party rejected all of the Soviet proposals regarding the land swap. After the failed negotiations with Finland, the two countries broke diplomatic relations on November 29, 1939. Soon, on November 30, Joseph Stalin ordered the Soviet troops to cross the Finnish border, and the President of Finland, Kyösti Kallio, declared war against the Soviet Union.

The Red Army crossed the Finnish border on November 30, 1939, with 21 divisions and 450,000 soldiers. Finland managed to mobilize an army of 250,000.

Joseph Stalin ordered the mobilization of more than one million Red Army soldiers across the Finnish border, while Finland had only 33,000 to begin with. The Soviets deployed 2,300 aircraft, the Finns just 114, and Russia had almost 6,000 tanks to Finland’s 32.

Due to his apparent military superiority, Joseph Stalin anticipated an easy and quick victory. However, Finland showed unprecedented and unexpected resistance and managed to push back the Soviet army for three months. In addition, the Red Army appeared to be poorly equipped and unprepared. Nearly 50% of army officers were executed during Stalin’s purge of the Red Army in 1937. The senior officers’ inexperience also played a key role in the Finns’ initial successful resistance. At the same time, the Red Army was poorly equipped. Many of the combatants experienced frostbite rather than war injuries because their clothing did not match the region’s climatic conditions.

Military operations during the Winter War were stretched on three fronts, the most crucial of which was the Karelian Isthmus due to its proximity to Leningrad. On this territory was positioned the most well-known Mannerheim Line, named after the Finnish Army’s then commander-in-chief, Field Marshal Baron Carl Gustaf Emil Mannerheim.

The Red Army attacked in the direction of the Mannerheim Line between November 30, 1939, and February 10, 1940. The military operations to break the Mannerheim Line started on February 11.

Despite a relatively small number, the Finnish military forces proved to be fierce adversaries. They were using guerilla tactics, and their knowledge of the local landscape and extreme winter conditions further contributed to the Finnish forces’ initial success.

Joseph Stalin’s plan for the short war in Finland was failing, and he was furious. Soviet propaganda was actively working to portray the Red Army’s failure as influenced by Finland’s harsh terrain and winter conditions. It also claimed that the United States had given Finland 1,000 of its best pilots to fight against the Soviet forces. But Finland’s initial success can be attributed to its fast ski troops and special maneuvers, also known as the “motti” tactic. Instead of attacking larger military groups, the Finns opted to divide the enemy into smaller units, making them more vulnerable.

One of the most famous Finnish inventions during the confrontations proved to be the “Molotov cocktail.” This creative weapon represented a handmade bottle firebomb directed toward the Soviet tanks, named after Vyacheslav Molotov, the Soviet foreign minister who played a key role in drafting and signing the Molotov-Ribbentrop Pact. The Molotov cocktails were actively used during the bombings. Molotov claimed the bombs to be “airborne humanitarian food deliveries” for their “starving” neighbors. Finns mockingly referred to the cluster bombs as “Molotov bread baskets,” whereas “Molotov cocktail” could be “a drink to go with his food parcels.”

The Finns also adopted a wait-and-see approach. Their ultimate goal was to hold out until either the West intervened to save them or the Soviets accepted a diplomatic settlement. Thirteen states expressed support for Finland during the war, sending armaments, with major suppliers being Sweden, France, the United States, and Great Britain. However, by March 1940, the Finnish leaders realized that limited outside support would not be enough. The existing poor economic and tense political environment pushed major countries to avoid conflict, especially with one of the great power, the Soviet Union. In addition, Finland’s geopolitical location made it difficult for other countries to provide logistical support.

The Soviets broke through the Mannerheim Line in February 1940 using heavy artillery bombardments. They continued to advance to the Finnish city of Viipuri (Vyborg). The possibility of a total takeover of Finland became a reality. Either the Soviet Union would seize Finland, a pro-Soviet administration would take power, or the Finns could try to initiate the negotiations for the settlement of the conflict with a relatively less damaging outcome.

The Finnish government opted for the cease-fire agreement. As a result, the Moscow Peace Treaty was negotiated and signed on March 12, 1940, in Moscow, Russia. According to the conditions of the treaty, a new border was drawn between Finland and the Soviet Union. The entire Karelian Isthmus, along with other strategic islands, was now in Soviet possession, acquiring about 10% of Finland’s pre-war territory and 20% of its industrial capacity. On the other hand, the Soviets withdrew their forces from the Petsamo (Pechenga) territory that they had ceded to Finland in 1920. Twelve percent of Finland’s population—around 422,000 Karelians—were forced to flee their homes.

The Winter War lasted 105 days and was brutal, resulting in significant casualties for both sides. However, due to the limited resources available, accurate casualty figures can be difficult to determine. It is estimated that around 126,000 Soviet soldiers were killed or went missing during the conflict, with an additional 264,000 wounded or sick. Around 25,000 Finnish soldiers were killed or went missing during the war, with an additional 44,000 wounded.

The Winter War had significant consequences for both countries as well as for the wider geopolitical landscape of Europe. The Soviets, anticipating a swift victory, suffered much higher casualties than expected and were ultimately forced to settle for a partial victory. It also threatened the reputation of the Soviet Union. The international community widely condemned the brutality of the conflict, resulting in the banning of the Soviet Union in the League of Nations on December 14, 1939.

The Winter War and its consequences had implications for the wider European and global geopolitical environment as well. The Soviet Union’s setbacks in the war may have influenced Adolf Hitler’s decision to launch Operation Barbarossa, his invasion of the Soviet Union in 1941.

The Winter War had a profound impact on Finnish society as well, shaping its national identity and memory. The war is still celebrated as a symbol of Finnish resilience and courage, and its legacy can be seen in Finnish culture, politics, and society to this day.