In late 1942, the Allies had taken the offensive against Germany but the dispatch of supplies to the USSR by convoy via the Arctic route was suspended, due to the demands of the Mediterranean campaign.

Discussions between the British Prime Minister Winston Churchill and the US President Franklin D. Roosevelt led to ships being dispatched independently to Russia from Iceland as a substitute for Convoy PQ 19, using the polar night of the Arctic winter for concealment.

In large convoys, the commodore was assisted by vice- and rear-commodores who directed the speed, course and zig-zagging of the merchant ships and liaised with the escort commander.

[3] Due to the losses of Convoy PQ 18 (2–21 September) in the Arctic and Operation Torch (8–16 November) in the Mediterranean, for which more than 500 ships had to be escorted, much of the British Home Fleet was sent south.

[5] The British Government Code and Cypher School (GC&CS) based at Bletchley Park housed a small industry of code-breakers and traffic analysts.

In 1941, B-Dienst read signals from the Commander in Chief Western Approaches informing convoys of areas patrolled by U-boats, enabling the submarines to move into "safe" zones.

[9] In early September, Finnish Radio Intelligence deciphered a Soviet Air Force transmission which divulged the convoy itinerary and forwarded it to the Germans.

[10] In the Arctic autumn, the hours of daylight diminished until by midwinter there was only twilight at noon, conditions in which convoys had the best chance of evading German aircraft, ships and U-boats.

[11] Frederich Engels sailed on 11 August and Belomorkanal followed next day, both reaching Archangel, which increased optimism at the Admiralty, that the slower merchant ships that had been part of PQ 19 could emulate the feat in the lengthening Arctic nights.

On return the ships carried the aircrew and ground staff of the two Hampden torpedo-bomber squadrons based in Russia during Operation Orator in September.

[12] From 24 to 28 September, the German cruiser Admiral Hipper and five destroyers conducted Operation Zarin, a sortie to mine the west coast of Novaya Zemlya.

[13] On 5 November, Admiral Hipper sailed again with the 5th Destroyer Flotilla comprising Z29, Z30, Friedrich Ekoldt and Richard Breitzen, after receiving information from aircraft and U-boats, that individual Allied ships were running the gauntlet through the Barents Sea.

[16] In November, Luftflotte 5, the German air command in Norway and Finland, was ordered to transfer its Ju 88 and He 111 bombers and torpedo-bombers to the Mediterranean against Operation Torch, a decision which the British received through Ultra intercepts.

Only the Heinkel 115 floatplanes, suitable for torpedo attacks on stragglers and some Ju 87 dive-bombers remained in Norway, along with a few long-range reconnaissance aircraft to observe for the surface and U-boat forces.

Junkers Ju 88s of I/KG 30 summoned to the scene, bombed and sank the Soviet ship Dekabrist and II/KG 30 damaged Chulmleigh and William Clark, which was finished off by U-354 (Kapitänleutnant Karl-Heinz Herbschleb) later that day.

Chulmleigh went aground on the Sørkapp (South Cape) of Spitzbergen, the main island of Svalbard; unable to refloat and disabled by the bombing, it was abandoned and torpedoed by U-625 on 16 November.

Baku was badly damaged in the storm but managed to limp back to port; a large wave hit Sokrushitelny and ripped off the stern.