The war against Germany was started officially but reluctantly in September 1944. It turned into a real war by the beginning of October. 

One of the terms of peace was that Finland should expel the 200,000-strong German troops out of Finnish territory within two weeks. The Germans initially started pulling out in September, in collaboration with Finns. The Soviet Union thought the withdrawal was taking too long, and so the war which had started out as a pretend war became a fully fledged war in October 1944 when Finns attacked Germans in Tornio.

As far as Germany was concerned, this was an act of betrayal by a former brother-in-arms. In response, an order was issued to destroy Lapland, which is what the Germans systematically did as they withdrew from Finland. They annihilated almost every building, road, bridge and form of marine transport found in Lapland. 

Since another of the peace term was the disbanding of the field army, the expulsion of the Germans was down to the regular personnel and 19–20-year-old conscripts. The last Germans to withdraw from Finland left as late as April 1945.