In the winter of 1939, the Soviet Union launched an invasion to annex Finland. Despite their numerical superiority, the Soviets were unable to overwhelm the Finns. In the spring of 1940, the two sides signed the Moscow Peace Treaty, resulting in minor territorial gains. Peace between the two nations would not last long. Finland’s relationship (termed co-belligerence as opposed to alliance) with Nazi Germany would spark a second war (Continuation War) at the launch of Operation Barbarossa in June 1941. With the massive assault across Eastern Europe, the Soviet Union was forced to withdraw troops along the Finnish border to strengthen front-line units. As a result of the deteriorated lines, Finland initiated an offensive to retake their lost territory.
As the Germans swept across the Soviet Baltic region, Finnish troops were staged on the outskirts of Leningrad. The Finns deployed 16 divisions along the Karelian Isthmus, tying down Soviet troops that could have supported the defense of Leningrad. Despite German insistence of a Finnish assault during the Siege of Leningrad, Finland’s Field Marshall C.G.E. Mannerheim refused. Throughout the two-year siege of the city, Finnish troops remained deployed in the Karelian Isthmus, eventually reducing its strength to seven divisions.
On 9 June 1944, the Soviets initiated the Vyborg-Petrozavodsk Offensive against Finnish defenses in the Karelian Isthmus. The Soviets were able to retake the territory lost in 1941 and by August 1944, Finland began to seek a way out of the war. With a renewed peace treaty, the Soviets regained their territory from the Winter War and forced Finland to pay $300 million in war reparations. As a result of the armistice, Finland was compelled to oust the German troops remaining in their territory. This led to the instigation of the Lapland War between Finland and Germany.
The Germans had over 200,000 troops deployed in Finland at the beginning of the Lapland War. German troops were forced to retreat into northern Norway while also engaging the aggressive Finnish offensive. One of the largest battles during this period occurred in region near the town of Tornio. The Germans captured 262 civilians, and threatened the Finnish government they would execute them if German POWs were not released. The plan backfired when Finnish commanders reported they would execute all German prisoners if any civilian were harmed by the German troops. The Germans released the civilians and abandoned Tornio. By spring 1945, the bulk of German forces had retreated, allowing Finland to demobilize its military and rebuild its nation from nearly six years of war.