The 'Battle of Petsamo' was fought between Soviet and Finnish forces in the extreme north of Finland as the northernmost element of the Soviet offensive known to the Finns as the 'Talvisota' winter war (30 November 1939/12 March 1940).
The Finnish forces, totalling a mere three companies, were greatly outnumbered but managed sometimes to contain and generally to slow the Soviet troops as a result of their exploitation of the extreme terrain, difficult weather and excellent tactical leadership.
The Finnish troops comprised the 10th Separate Company (10th Er.K.) in Parkkina and the 5th Separate Battery (5th Er.Ptri.) with four 76-mm (3-in) guns, dating from 1887 in Liinahamari. The separate company and battery belonged to no specific division of the Finnish army, and could be considered as ad hoc units for wholly detached service. The units were part of the Finnish army’s Lapin Ryhmä (Lapland Group) headquartered in Rovaniemi. The troops were later reinforced with the 11th Er.K. and the 3rd Er.K. which were not part of Finland’s original mobilisation plans. Another later addition was the small 11th Tiedusteluosasto (11th Reconnaissance Group). All these units, totalling fewer than 900 men, constituted the Osasto 'Pennanen' ('Pennanen' Detachment) commanded by Kapteeni Antti Pennanen.
The USSR had in the Kola peninsula’Komkor Valerian A, Frolov’s 14th Army of Komandarm 2a ranga Kyrill A. Meretskov’s Leningrad Military District. The army comprised the 104th Division, [e[52nd Division and 14th Division]e], totalling totalling some 52,500 men. Only the 104th Division and 52nd Division took part in the operation to take Petsamo, the 14th Division[/e being retained to occupying Liinahamari harbour. The Soviets had an overwhelming superiority in troops in the area, but most Soviet troops were preparing to fight against a possible British and French landing near Murmansk and were not involved in the fight against Finland.
Elements of the 104th Division crossed the border into Finland on 30 November 1939 and occupied the Finnish part of the Rybachiy peninsula. The division’s 242nd Regiment reached Parkkina on 1 December as the Finnish troops withdrew to Luostari. The 52nd Division was moved to Petsamo by sea, took over the main role in the offensive and pushed the Osasto 'Pennanen' back to Höyhenjärvi, where the Soviet attack was halted on 18 December. During the following two months the Soviet forces remained inactive. During this time the Finns made several reconnaissance and guerrilla raids behind the Soviet lines. After the two-month pause, the Soviet advance continued and this time attacks on 25 February forced the Finnish troops back to Nautsi near the Inari kake, and here the Soviet forces remained for the rest of the 'Talvisota'.
by the terms of the Moscow Peace Treaty of 12 March 1940, Finland had to cede parts of its territory to the USSR, and among these areas was the Finnish part of the Rybachiy peninsula in the extreme north of the Petsamo region. The USSR took the whole of the Petsamo area after the 'Jatkosota' continuation war.