'PQ' (i) was the designation of Allied convoys (together with a numerical suffix) plying the route from Iceland to ports in the northern part of the USSR, and as such reciprocals of the 'QP' series (September 1941/September 1942).

There were 19 such convoys before the series was replaced by the 'JW' series, departing from Loch Ewe on the west coast of Scotland.

PQ.1 was in fact the second of the convoys, undertaken after the concept had been proved in 'Dervish', via the Arctic route to ports in the northern part of the USSR for the delivery of war matériel: this convoy sailed from the Hvalfjörður in south-western Iceland on 29 September 1941 and reached at Arkhangyel’sk on 11 October 1941, and comprised 10 merchant ships loaded with raw materials, 20 tanks and 193 crated Hawker Hurricane fighters. Supported by the auxiliary oiler Black Ranger, the convoy was escorted by 10 British warships in the form of the heavy cruiser Suffolk, the destroyers Antelope, Anthony, Escapade and Impulsive, and the minesweepers Britomart, Gossamer, Harrier, Hussar and Leda. All of the ships arrived safely.

PQ.2 was the third convoy via the Arctic route to the northern USSR, and took place between 13 October and 30 October 1941. The merchant vessels of the convoy departed Liverpool on 13 October and reached Arkhangyel’sk without loss on 30 October. The convoy comprised six merchant ships and was escorted by British warships in the form of the heavy cruiser Norfolk, the destroyers Icarus and Eclipse, and five minesweepers.

PQ.3 was the fourth convoy via the Arctic route to the northern USSR, and took place between 9 and 22 November 1941). The convoy departed the Hvalfjörður in Iceland on 9 November 1941 and reached Arkhangyel’sk without loss on 22 November. The convoy comprised six British and two Panamanian merchant ships, and was escorted by British warships in the form of the light cruiser Kenya, the destroyer Intrepid, and a number of minesweepers and armed trawlers. The merchant vessel Briarwood returned to Iceland with damage from ice.

PQ.4 was the fifth convoy via the Arctic route to the northern USSR, and took place between 17 and 29 November 1941. The convoy sailed from the Hvalfjörður on 17 November 1941 and reached Arkhangyel’sk without loss on 28 November 1941. The convoy comprised four British and four Soviet merchant ships, and the escort consisted of British warships in the form of the heavy cruiser Berwick, the destroyers Offa and Onslow, two minesweepers and two armed trawlers.

PQ.5 was the sixth convoy via the Arctic route to the northern USSR, and took place between 27 November and 13 December 1941. The convoy sailed from the Hvalfjörður on 27 November 1941 and reached Arkhangyel’sk without loss on 13 December 1941. The convoy comprised five British and two Soviet merchant ships, the close escort comprised four British minesweepers, and distant cover was provided by the light cruiser Sheffield.

The last convoy of this series was PQ.18 of 2/21 September 1942 from Loch Ewe to Arkhangyel’sk with 48 merchant vessels and an eventual total of 74 escorts. The convoy departed Loch Ewe on the west coast of Scotland on 2 September 1942 and reached Arkhangelsk on 21 September 1942.

Following the disastrous losses suffered by the preceding PQ.17 convoy, the British were determined to provide the PQ.18 convoy with air cover, and the new escort carrier Avenger, recently arrived from construction in the USA, formed the core of the escort force. The departure of the convoy was postponed because a large part of the available British naval strength was engaged in the protection of the 'Pedestal' convoy carrying vital supplies to Malta in August.

The convoy comprised 40 merchant ships (11 British, 20 US, six Soviet and three Panamanian 1), four fleet auxiliaries, two oilers, one rescue ship and one CAM-ship carrying a single catapult-launched Hawker Hurricane fighter. Three ships which travelled only as far as Reykjavik were the 5,432-ton US Gateway City, 6,854-ton US Oremar and 5,582-ton British San Zotico. The four Soviet ships joined the convoy in Iceland, as too did the 7,191-ton US Richard Bassett, which later had to turn back with engine problems.

The close escort was provided by a force led by Commander A. B. Russell in the destroyer Malcolm, and otherwise comprised the destroyers Achates and Amazon, auxiliary anti-aircraft 'gun ships' Alynbank and Ulster Queen, corvettes Bergamot, Bryony, Bluebell and Camellia, anti-submarine trawlers Cape Argona, Cape Mariato, Daneman and St Kenan, and minesweepers Gleaner, Harrier and Sharpshooter. The escort was supported by a carrier group comprising the escort carrier Avenger and her accompanying escort destroyers Wheatland and Wilton), and a 'Fighting Destroyer Escort' of the destroyers Ashanti, Eskimo, Faulknor, Fury, Impulsive, Intrepid, Marne, Martin, Meteor, Milne, Offa, Onslaught, Onslow, Opportune, Somali and Tartar commanded by Rear Admiral R. L. Burnett in the light anti-aircraft cruiser Scylla. The ocean escort force was augmented by local escort forces from Britain to Iceland (the destroyers Campbell, Echo, Eskdale, Farndale, Mackay, Montrose and Walpole, and trawlers Arab, Duncton, Hugh Walpole, King Sol and Paynter) and from Murmansk (the Soviet destroyers Gremyashchiy, Kuybyshev, Sokrushitelnyi and Uritskiy, and British minesweepers Britomart, Halcyon, Hazard and Salamander).

Distant cover was provided by Vice Admiral B. A. Fraser’s 'Heavy Cover Force' (the battleships Anson and Duke of York, light cruiser Jamaica, and destroyers Bramham, Broke, Campbell, Keppel, Mackay and Montrose) and Vice Admiral S. S. Bonham-Carter’s 'Cruiser Cover Force' (heavy cruisers London, Norfolk and Suffolk, and destroyers Bulldog and Venomous).

At the same time the Royal Navy sent two forces to Spitsbergen, one to deliver reinforcements for the garrison there (the heavy cruiser Cumberland, light cruiser Sheffield and destroyer Eclipse), and the other as a replenishment group for the convoy (the fleet auxiliary oilers Blue Ranger and Oligarch, destroyers Windsor and Worcester, and escort destroyers Cowdray and Oakley). To guard against a sortie by the German surface fleet in Norway a submarine patrol force was sent to keep watch on the main Norwegian ports, these nine boats being Shakespeare, Sturgeon, Tigris, Tribune, Unique, Unrivalled, Unshaken, Free French Rubis and Free Norwegian Uredd.

Opposing this armada, the Germans had established the 'Eispalast' U-boat patrol line of 12 boats (U-88, U-255, U-377, U-378, U-403, U-405, U-408, U-435, U-457, U-589, U-592 and U-703) in the Norwegian Sea and under Vizeadmiral Oskar Kummetz a surface force comprising the heavy cruiser (ex-pocket battleship) Admiral Scheer, heavy cruiser Admiral Hipper, light cruiser Köln and destroyers Richard Beitzen, Z 23, Z 27, Z 29 and Z 30 of Kapitän Gottfried Pönitz’s 8^th Zerstörer-Flottille.

Since the 'Rösselsprung' (i) foray against the preceding PQ.17 convoy during the summer, the battleship Tirpitz, heavy cruiser (ex-pocket battleship) Lützow and three destroyers had entered dock for repairs, which left the surface force depleted in numbers and strength.

The PQ.18 convoy was the first Arctic convoy supported by an escort carrier, Avenger carrying 10 Sea Hurricane fighters and three Fairey Swordfish torpedo bombing/anti-submarine aircraft.

A combined Royal Air Force and Royal Australian Air Force detachment, comprising 32 Handley Page Hampden torpedo bombers from Nos 144 and 455 Squadrons, nine Consolidated Catalina long-range patrol flying boats from No. 210 Squadron and three Supermarine Spitfire photo-reconnaissance aircraft, was also sent to air bases in the USSR to fend off any attack by major German surface warships, should such an undertaking eventuate. Nine of the Hampden aircraft were lost en route, including one which crashlanded in German-occupied Norway, and the plan for the operation thus fell into German hands. The British and Australian force regrouped at Vaenga air base, some 25 miles (40 km) to the north of Murmansk.

Generaloberst Hans-Jürgen Stumpff’s Norway-based Luftflotte V fielded a force of 42 Heinkel He 111 torpedo bombers of Oberst Martin Harlinghausen’s Kampfgeschwader 26 and 35 Junkers Ju 88 dive-bombers of Oberstleutnant Erich Bloedorn’s KG 30. The German tactical method was based on simultaneous attack by torpedo bombers and dive-bombers to swamp the defences, while Hauptmann Möller’s III/KG 26 was trained in the so-called 'golden comb' anti-convoy tactic of massed torpedo attack.

The PQ.18 convoy departed Loch Ewe on 2 September 1942, in the charge of its local escort force. On 7 September it was joined by the close escort force, together with eight merchant vessels from Reykjavík, while the local escort, with three merchant vessels, detached to Iceland. On 9 September the convoy was joined by Burnett in Scylla with the fighting destroyer escort forces, accompanied by the carrier Avenger and her group, which was to escort the convoy on to Arkhangyel’sk. The distant cover and cruiser cover forces had sailed independently, as had the two groups bound for Spitsbergen.

On 8 September a German reconnaissance aeroplane sighted, but then lost, the convoy. Contact was also made by some of the boats in the U-boat patrol line, and these started to shadowing. These were chased by the destroyers, in order to shake off pursuit, and on 12 September Kapitänleutnant Heino Bohmann’s U-88 was detected, attacked and sunk by Faulknor. By 13 September there were eight U-boats in contact, and during the morning of that morning Kapitänleutnant Reinhard von Hymmen’s U-408 sank Oliver Ellsworth and Stalingrad. At this stage the PQ.18 was some 150 miles (240 km) to the north-west of Bjornøya, about to turn into the Barents Sea. On this day the escort force was rejoined by Scylla and a number of destroyers which had previously been detached to refuel in Lowe Sound (otherwise Van Mijenfjorden) in Spitsbergen. This brought the escort up to full strength for the next leg of the voyage.

Also on 13 September the convoy was again sighted by a reconnaissance aeroplane, in this instance a Blohm und Voss Bv 138 flying boat from Banak in northern Norway. The air units based at Banak now mounted a full assault on the convoy, using the new 'golden comb' tactic. This involved a massed torpedo attack by full group of torpedo bombers, and resulted in the sinking of another eight of the convoy’s ships. Two more air attacks followed, but failed to score any hits. In all, eight aircraft were shot down on this day.

On the following day, 14 September, the attack was repeated, but on this occasion the escort force used tactics to counter the 'golden comb', and the combination of concentrated fire from the convoy and fighter attacks, the result of aggressive handling by the 'gun ship' Ulster Queen and carrier Avenger, broke apart the attack. Three air attacks resulted in the loss of one ship hit and the shooting down of 21 aircraft. On the same day there were more U-boat attacks. The tanker Atheltemplar was torpedoed and damaged by U-408 and then by Korvettenkapitän Karl Brandenburg’s U-457, and was finally abandoned and later sank. In counterattacks Korvettenkapitän Hans-Joachim Horrer’s U-589 was sunk by Onslow.

On 15 September there were further air attacks, but these were beaten off without loss. On this day there were still three U-boats in contact and another 12 in the area, and while these made several attempts to attack they had no success.

On 16 September Brandenburg’s U-457 was sunk by Impulsive, and during the afternoon of the same day the U-boat effort was terminated. Later the same day Burnett with Scylla and the destroyer escort, together with Avenger‍ '​s group, detached to meet and escort the homeward-bound QP.14 convoy, while the PQ.18 convoy continued with its close escort. On the following day it met the western local escort, a group of Soviet destroyers from Murmansk.

During this period the German surface force had no impact on the convoy operation. It had been alerted when the convoy was first sighted, and on 10 September had moved to the north into the Altafjord in preparation for a sortie. The move had been sighted by the British submarine patrol, and the Tigris made an unsuccessful torpedo attack on Admiral Scheer. The German surface warship force concentrated in the Altafjord, but Adolf Hitler, reluctant to risk the loss of any of his capital ships, refused to authorise an attack on the convoy, and on 13 September the sortie was cancelled.

The PQ.18 convoy was not yet out of danger, however. On 18 September it was attacked again by German aircraft: Kentucky was sunk and three German aircraft were shot down. Another air attack in the course of the following day scored no hits, and later on 19 September the PQ.18 convoy entered the White Sea after losing 13 of its ships.

The British and Australian force of Hampden aircraft undertook one patrol, on 14 September, and then left its 23 aircraft in the USSR before returning to the UK.

The PQ.18 convoy was seen as a success by the Allies, for while 13 ships had been lost, another 28 arrived safely, and the Arctic convoy route, which had been suspended since the destruction of the PQ.17 convoy, had been re-established. Furthermore, three U-boats had been destroyed, and 40 German aircraft had been shot down.

Whilst the Germans could be satisfied with the losses they had inflicted, they had to appreciate that they failed to stop the convoy getting through, and their own losses, particularly in trained pilots, were severe, denting the ability of the Luftwaffe to hinder future convoys. The German surface force had also been powerless to interfere, and its next venture, the 'Regenbogen' (i) sortie against the JW.51B convoy, would be a debacle resulting in the Battle of the Barents Sea.