During World War II, the Lapland War saw fighting between Finland and Nazi Germany – effectively from September to November 1944 – in Finland's northernmost region, Lapland. Though the Finns and the Germans had been fighting together against the Soviet Union since 1941 during the Continuation War (1941–1944), peace negotiations between the Finnish government and the Allies of World War II had been conducted intermittently during 1943–1944, but no agreement had been reached. The Moscow Armistice, signed on 19 September 1944, demanded that Finland break diplomatic ties with Germany and expel or disarm any German soldiers remaining in Finland.
The Wehrmacht had anticipated this turn of events and planned an organised withdrawal to Nazi-occupied Norway, as part of Operation Birke (Birch). Despite a failed offensive landing operation by Germany in the Gulf of Finland, the evacuation proceeded peacefully at first. The Finns escalated the situation into warfare on 28 September after Soviet pressure to adhere to the terms of the armistice. The Finnish Army was required by the Soviet Union to push Wehrmacht troops out of Finnish territory. After a series of minor battles, the war came to an effective end in November 1944, when all of the Wehrmacht troops had reached Norway or the border area and took fortified positions. The last Wehrmacht soldiers left Finland on 27 April 1945, shortly before the end of World War II in Europe.
The Finns considered the war a separate conflict because hostilities with other nations had ceased after the Continuation War. From the German perspective, it was a part of the two campaigns to evacuate from northern Finland and northern Norway. Soviet involvement in the war amounted to monitoring Finnish operations, minor air support and entering northeastern Lapland during the Petsamo–Kirkenes offensive. The military impact was relatively limited with each side sustaining around 4,000 in total casualties, although the Germans' delaying scorched earth and land mine strategies devastated Finnish Lapland. The Wehrmacht successfully withdrew, and Finland upheld its obligations under the Moscow Armistice, but it remained formally at war with the Soviet Union and the United Kingdom until ratification of the 1947 Paris Peace Treaty.
Germany and Finland had been at war with the Soviet Union (USSR) since Operation Barbarossa began in June 1941, co-operating closely in the Continuation War and Operation Silver Fox with the German 20th Mountain Army (German: 20. Gebirgsarmee) stationed in Lapland. As early as mid-1943, the German high command Oberkommando der Wehrmacht (OKW) began to plan for the eventuality that Finland might negotiate a separate peace agreement with the Soviet Union. The Germans planned to withdraw their forces northward in order to shield the nickel mines near Petsamo (Russian: Pechenga). During the winter of 1943–1944, the Germans improved the roads from northern Norway to northern Finland by extensive use of prisoner-of-war labour in certain areas. Casualties among the labouring prisoners were high, in part because many of them had been captured in southern Europe and were still in summer uniform. The Germans also surveyed defensive positions and planned to evacuate as much materiel as possible from the region, and meticulously prepared for withdrawal. On 9 April 1944, the German withdrawal plan was designated as Operation Birke. In June 1944, the Germans started to construct fortifications against a possible enemy advance from the south. The accidental death of Generaloberst Eduard Dietl on 23 June 1944 brought Generaloberst Lothar Rendulic to the command of the 20th Mountain Army.
After the Soviet strategic Vyborg–Petrozavodsk offensive in southern Finland from June to July and a change in Finnish leadership in August 1944, Finland negotiated a separate peace agreement with the USSR. The ceasefire agreement required the Finns to break diplomatic ties with Germany and publicly demand the withdrawal of all German troops from Finland by 15 September 1944. Any troops remaining after the deadline were to be expelled or disarmed and handed over to the USSR. Even with the German withdrawal operation, the Finns estimated it would take three months for the Wehrmacht to fully evacuate. The task was further complicated by the Soviet demand that the majority of the Finnish Defence Forces be demobilised while conducting a military campaign against the Germans. Before deciding to accept the Soviet demands, President Carl Gustaf Emil Mannerheim, former Finnish commander-in-chief, wrote a letter directly to Adolf Hitler:
Our German brothers-in-arms will forever remain in our hearts. The Germans in Finland were certainly not the representatives of foreign despotism but helpers and brothers-in-arms. But even in such cases foreigners are in difficult positions requiring such tact. I can assure you that during the past years nothing whatsoever happened that could have induced us to consider the German troops intruders or oppressors. I believe that the attitude of the German Army in northern Finland towards the local population and authorities will enter our history as a unique example of a correct and cordial relationship [...] I deem it my duty to lead my people out of the war. I cannot and I will not turn the arms which you have so liberally supplied us against Germans. I harbour the hope that you, even if you disapprove of my attitude, will wish and endeavour like myself and all other Finns to terminate our former relations without increasing the gravity of the situation.
The 20th Mountain Army had been fighting the Soviet Karelian Front since Operation Barbarossa along the 700 km (430 mi) stretch from the Oulu River to the Arctic Ocean. It now comprised 214,000 soldiers, a considerable amount of them under Schutzstaffel (SS) formations, led by Generaloberst Rendulic. The number of active troops decreased quickly as they withdrew to Norway. The army had 32,000 horses and mules and 17,500–26,000 motorised vehicles as well as a total of 180,000 t (200,000 short tons) in rations, ammunition and fuel to last for six months. The army was positioned as follows:
XIX Mountain Corps (German: XIX Gebirgskorps) in the far-northern Petsamo area beside the Arctic Ocean.
XXXVI Mountain Corps in the area of Salla and Alakurtti, eastern Lapland.
XVIII Mountain Corps was in charge of the southern flank at Kestenga and Uhtua.
The III Corps (Finnish: III armeijakunta, III AK), led by Lieutenant General Hjalmar Siilasvuo, gradually shifted from the defence of the Vyborg–Petrozavodsk Offensive to the latitude of Oulu and was fully repositioned by 28 September. The III Corps consisted of the 3rd, 6th, and 11th Divisions as well as the Armoured Division. Additionally, four battalions formerly under German command were converted into separate detachments. Two regiments, Infantry Regiment 15 and Border Jaeger Regiment, reinforced the III Corps. In total, Finnish ground forces in the Lapland theatre were 75,000 strong. The number of Finnish troops dropped sharply as the Germans withdrew and the Finnish Army was demobilised; by December 1944 only 12,000 were left. Due to this, the Finnish soldiers were mostly conscripts, as veterans were transferred away from the front. The latter part of the war was therefore dubbed the "Children's Crusade" (Finnish: lasten ristiretki) in Finland.
Evacuation and naval operations in September
The announcement on 2 September 1944 of the ceasefire and the Moscow Armistice between Finland and the USSR triggered frantic efforts by the 20th Mountain Army, which immediately started Operation Birke. Large amounts of materiel were evacuated from southern Finland and harsh punishments were set for any hindering of the withdrawal. The Germans began to seize Finnish shipping. Finland responded by preventing ships sailing from Finland to Germany and nearly doomed the materiel evacuations of Operation Birke. So the order was rescinded and then the Finns, in turn, allowed Finnish tonnage to be used to hasten the German evacuations. The first German naval mines were laid in Finnish seaways on 14 September 1944, allegedly for use against Soviet shipping, though since Finland and Germany were not yet in open conflict, the Germans warned the Finns of their intent.