'Strength' was the British naval undertaking to facilitate the passage of the PQ.1 Arctic convoy from the Hvalfjörður in south-western Iceland to Arkhangyel’sk in the northern USSR (29 September/11 October 1941).

Comprising 11 ships carrying 193 crated Hawker Hurricane fighters, 20 tanks and raw materials, the convoy was the second, following 'Dervish', to make the run to a port in the northern USSR, and was escorted by the heavy cruiser Suffolk, destroyers Impulsive and, for a time, Anthony, Antelope and Escapade, and minesweepers Britomart, Gossamer, Harrier, Hussar and Leda. The Germans did not detect the convoy, all of whose vessels therefore arrived safely.

The QP.1 return convoy, with 14 unladen ships accompanied by the heavy cruiser London and escorted by the destroyers Active, Anthony and Electra, and trawlers Hamlet, Macbeth and Ophelia, made the passage from Arkhangyel’sk to Scapa Flow in the Orkney islands group between 28 September and 10 October. Local escort was provided in the White Sea by Soviet patrol ships of the White Sea Flotilla, and off the Kola inlet by the British minesweepers based temporarily in northern Russia.

Cover for the PQ.1 and QP.1 convoys was provided by the old carrier Argus returning from 'Dervish', the heavy cruiser Shropshire and the destroyers Matabele, Punjabi and Somali (Force 'L'), and more distant cover was provided by the fleet carrier Victorious, the heavy cruiser Devonshire and the destroyers Eclipse, Escapade and Inglefield (Force 'M').