'Church' (i) was a British unrealised plan to destroy the Arctic port of Petsamo as a means of halting or at least hindering nickel ore shipments to Germany (July 1940).

This part of Finland had been seized by the Soviets in one of their few major success in the Soviet-Finnish 'Talvisota' of 1939/40, but then returned to Finland by the Treaty of Moscow that ended this 'Winter War' on 12 March 1940. By the terms of the Russo-German treaty of August 1939, areas such as eastern Poland, the Baltic states (initially Estonia and Latvia, but later Lithuania as well) and Finland were assigned to the Soviet sphere of influence.

This persuaded the Soviet dictator, Iosif Stalin, that he thus possessed the opportunity to demand from Finland a number of territorial and sovereignty concessions, including the Karelian isthmus between the Gulf of Finland and Lake Ladoga as far to the north-west as Viipuri, four small islands in the Gulf of Finland, the use of the Hanko peninsula at the mouth of the Gulf of Finland as a Soviet naval and air base, and lastly the Finnish half of the Rybachy peninsula, including Petsamo, in the far north.

The Finns refused, and it was this which triggered the 'Talvisota' launched by the Soviets on 30 November 1939. In the far north the Finns were heavily outnumbered but managed to contain the Soviet troops as a result of their superior exploitation of factors such as the extremes of terrain and weather. The Finnish troops comprised the Erillinen Komppania 10 (10^th Detached Company) in Parkkina and the Erillinen Patteri 5 (5^th Detached Battery) in Liinahamari. These independent units were not allocated to any specific force or formation, but could be used in ad hoc forces. The troops were part of the Finnish army’s Lapin Ryhmä (Lapland Group), which had its headquarters at Rovaniemi, and were later reinforced by the Erillinen Komppania 11 and a third company which was not part of the original Finnish mobilisation scheme. Another unit later added to this strength was the Tiedusteluosasto 11 (11^th Reconnaissance Group), and this grouping of fewer than 900 men was designated as the Osasto 'Pennanen' ('Pennanen' Detachment) after its commander, Captain Antti Pennanen.

In the far north the USSR had on the Kola peninsula General Major Valerian A. Frolov’s 14^th Army comprising the 14^th Division, 52^nd Division and 104^th Division. Of these, only the 52^nd Divisionand 104^th Division were involved in the 'Battle for Petsamo'. The Soviets had an overwhelming superiority in troops in the area. Elements of the 104^th Division crossed the border on 30 November and occupied the Finnish part of the Rybachy peninsula. The 242^nd Regiment of the 104^th Division reached Parkkina on 1 December, and the Finnish troops withdrew to Luostari. The 52^nd Division was moved to Petsamo by sea, and took over the offensive from the 104^th Division, pushing the Osasto 'Pennanen' back to Höyhenjärvi until the attack was halted on 18 December.

During the following two months the Soviet forces took no further action, and the Finnish troops made several reconnaissance and guerrilla raids behind the Soviet lines. After its two-month pause, the Soviets resumed their advance, and this time attacks on 25 February forced the Finnish troops back to Nautsi near the Inari lake, where the front stabilised until the war ended in an armistice.

With the restoration of Petsamo to Finland after the armistice, the German seizure of Norway in 'Weserübung' and the increasingly close alignment of Finland and Germany in the spring of 1940, there seemed every likelihood of the restoration of Finnish nickel ore shipments to Germany, and this was the spur for the initial concept of 'Church' (i), though subsequent assessment of the threat which would be posed to any such undertaking by German aircraft and warships based in northern Norway then paved the way to a more sanguine reassessment of the concept and its resulting abandonment.