The Russian Invasion of Finland, November 30, 1939

In the years leading up to the Soviet Union’s invasion of Finland in November 1939, the Soviet Union demanded that Finland cede substantial border territories in exchange for land elsewhere, claiming security concerns, primarily the protection of Leningrad, 32 km (20 miles) from the Finnish border. Finland refused to allow the Soviets to simply demand and steal parts of Finland’s homeland.

On November 30, 1939, just 75 days after the Soviet Union had invaded Poland, the Soviet Union invaded Finland, beginning the Winter War (Зимняя война). The war ended three and a half months later, on March 13, 1940, with the Moscow Peace Treaty.

The Finnish armed forces, despite being severely outnumbered and outgunned, especially in tanks and aircraft, fought bravely and brilliantly, and inflicted severe losses on the Soviet armed forces. The Soviet invasion of Finland made little progress. The League of Nations condemned the Soviet Union, declared the Soviet attack illegal, and expelled the Soviet Union from the League of Nations.

For more than two months, Finland successfully repelled Soviet assaults, inflicting substantial losses on the Russians in temperatures as low as −43 °C (−45 °F). The battles were fought mainly in Taipale, along the Karelian Isthmus, in Kollaa, in Ladoga Karelia, and on the Raate-Suomussalmi Road, in Kainuu. Battles were also fought in North Karelia and Lapland.

Following their initial failures, the Soviets reduced their strategic objectives. The Soviet military reorganized and adopted different tactics, renewed their offensive in February 1940, and eventually overcame the Finnish defenses on the Karelian Isthmus.

This left the Finnish army in the main theater of war near the breaking point, with a retreat seemingly inevitable. Finnish commander-in-chief Carl Gustaf Emil Mannerheim urged a peace deal with the Soviets, while the Finns still retained some bargaining power.

Hostilities were ceased in March 1940 with the signing of the Moscow Peace Treaty. Finland was forced to surrender 9% of its sovereign territory to the Soviet Union, especially substantial territories along Lake Ladoga and further north. Soviet gains actually exceeded their pre-war demands.

Finland retained its sovereignty and enhanced its international reputation. The international reputation of the Soviet Union declined significantly.

Soviet losses in manpower, equipment, and reputation were heavy. The poor performance of the Red Army confirmed negative Western opinions of the Soviet armed forces. This perceived weakness of the Soviet Union led German Führer und Reichskanzler Adolf Hitler to believe that an attack on the Soviet Union would be successful. Hitler convinced himself that Nazi Germany should invade the Soviet Union.

In the meantime, the Soviet Union looked around for another weaker country to exploit, and issued an ultimatum to Romania on June 26, 1940, threatening the use of force in another land grab act of aggression.

Two days later, the Soviet Union began the occupation of Bessarabia and Northern Bukovina between June 28 and July 3, 1940, simply absorbing these parts of Romania into the Soviet Union. On October 26, 1940, the Soviet armed forces also grabbed six Romanian islands on the Chilia branch of the Danube River.

Initially, the Soviet Union had planned a full-scale invasion to annex these parts of Romania, but the Romanian government, responding to the Soviet ultimatum of June 26, 1940, agreed to withdraw from their own sovereign territory to avoid military conflict with the Soviet Union.

Following the Soviet occupation of Romanian territory between June and October 1940, Adolf Hitler saw his opportunity to do the same thing to Russia, and the German High Command began planning for the invasion of the Soviet Union, which Hitler approved in December 1940.