The evacuation was a result of the 1940 Moscow Peace Treaty that concluded the Winter War, an attack of the Soviet Union on Finland. The actual evacuation started already in 1939, during the war. The treaty did not force Finland to empty the ceded territory, but almost nobody was willing to stay, taking their belongings with them. Only the buildings and machinery were to be left behind intact as per the Peace Treaty, which for the most part also took place.
During the Continuation War some 260,000 of the displaced population returned home. In June 1944, Finnish troops withdrew from the ceded areas again as a result of the Soviet Fourth strategic offensive. At the same time, the population was evacuated again.
The Paris Peace Treaties of 1947 finally confirmed the Finnish loss of the territory. The evacuees were permanently settled in Finland. The government of Finland subsidized the resettlement in two ways:
Since the 1990s some associations have been calling for returning Karelia back to Finland.