The military history of Finland during World War II encompasses three major conflicts. The first two of these – the defensive Winter War in 1939–1940, and the Continuation War alongside the Axis Powers in 1941–1944 – were waged against the Soviet Union. The third one, the Lapland War in 1944–1945, followed the signing of an armistice agreement with the Allied Powers, which stipulated expulsion of German forces from Finnish territory.
During World War II, Finland was in many ways a unique case:
- It was the only European country bordering the Soviet Union in 1939 which was still unoccupied by 1945.
- Of all the European countries fighting, only three European capitals were never occupied: Moscow, London and Helsinki.
- It was a country which sided with Germany, but in which native Jews and almost all refugees were safe from persecution.
- It was the only co-belligerent of Nazi Germany which maintained democracy throughout the war.
- It was also the only belligerent in mainland Europe to do so.
- During WWII, Finland fought in 3 separate wars. They were aided in the 2nd war (against the USSR) by Germany, while in the 3rd war (against Germany), they were aided by the USSR.
Although Finland was never de jure member of Axis powers, as it never signed the Tripartite Pact, it was a companion of Germany from the beginning of Operation Barbarossa 1941 to separate peace with the Soviet Union in 1944.
Finland, however, was never a strong supporter of Nazi Germany and felt that an alliance with Hitler would help ensure that the country would remain independent. Finland was led by its elected president and parliament during the whole 1939–1945 period. As a result, some political scientists name it as one of the few instances where a democratic country was engaged in a war against one or more other democratic countries, namely the democracies in the Allied forces.
However, it is worth pointing out that nearly all Finnish military engagements in World War II were fought solely against an autocratic power, the Soviet Union, and the lack of direct conflicts specifically with other democratic countries leads others to exclude Finnish involvement in World War II as an example of a war between two or more democracies.