As Germany invaded the Soviet Union in June 1941, Finland participated in the invasion primarily to recover the territories it was forced to cede to the USSR after the Moscow Peace Treaty which ended the Winter War between the Finns and the Soviets. Military success quickly resulted in the Finnish occupation of Eastern Karelia. Because of their Finno-Ugric heritage, the Finns were initially classified by Nazi racial experts as a people unrelated to the other Nordic countries, in spite of a long history of political unity with Sweden. As a result, the Swedish-speaking minority of Finland was favored at first over Finnish speakers for recruitment into the Finnish Volunteer Battalion of the Waffen-SS because they were categorically considered part of the "Nordic race".