'Doppelschlag' was a German unrealised naval operation to use heavy surface warships intercept and destroy the Allies' PQ.18 convoy from the UK to the northern ports of the USSR (September 1942).

The operation was thus the successor to 'Rösselsprung' (i) against the PQ.17 convoy in July 1942, and reflected the natural desire of the German navy to strike a comparable blow and thus, it was hoped, persuade the Western Allies of the impossibly high cost of trying to aid the Soviets by means of convoys through Arctic waters within range of German aircraft, surface warships and U-boats based in the northern part of occupied Norway.

In its early planning stage, 'Doppelschlag' resembled 'Rösselsprung' in that the forces involved would wait at readiness at their bases until a convoy was detected, while the U-boats of the 'Eispalast' wolfpack would establish a patrol line in the Norwegian Sea to give early warning of any convoy’s approach. Once the convoy had been detected, the surface ships would steam northward to the Altafjord and there await the order to sortie. The Germans' extreme sensitivity to the possibility of losing a capital ship in an engagement with a major Allied naval force meant that only Adolf Hitler could give permission for the second stage, namely the sortie into the Barents Sea. At sea, the German ships would divide into two battle groups, to attack the convoy from each side. It was envisaged that the first group would engage and draw off any Allied heavy warships with the convoy, while the second would attack the merchant ships without having to face serious opposition. It was this intended 'double blow' that inspired the operational name.

The forces intended to take part in the operation were the 'pocket battleship' Admiral Scheer, the heavy cruiser Admiral Hipper, the light cruiser Köln and six destroyers. Other German capital ships based in Norway, namely the battleship Tirpitz and the 'pocket battleship' Lützow, were unavailable for the operation as both had been undergoing repairs since the end of 'Rosselsprung'.

Thus for the purpose the Germans planned an operation based on a strong force of heavy and light warships, which would establish contact with the target convoy in a manner that had proved impossible in 'Rösselsprung' (i).

The Allies, meanwhile, had decided not to despatch their next Arctic convoy during the summer, when the almost continual light offered the Germans ideal conditions in which to locate and attack the convoy, and thus opted to delay the PQ.18 convoy until later in the year when the shorter days offered the merchant ships and their escorts a better opportunity to avoid detection and subsequent attack.

As a result the German forces spent more than two months at readiness before the PQ.18 convoy (11 British, three Panamanian, six Soviet and 20 US merchant ships including one tanker, as well as two oilers, one catapult-armed merchant ship and the rescue ship Copeland) departed Loch Ewe on the west coast of Scotland on 2 September.

Close escort was provided by a force 1 led by Commander A. B. Russell in the destroyer Malcolm and supported by an aircraft carrier group (the escort carrier Avenger accompanied by the escort destroyers Wheatland and Wilton), and a 'fighting destroyer escort' of 16 fleet destroyers (Ashanti, Eskimo, Faulknor, Fury, Impulsive, Intrepid, Marne, Martin, Milne, Meteor, Offa, Onslaught, Onslow, Opportune, Somali and Tartar) commanded by Rear Admiral R. L. Burnett in the light anti-aircraft cruiser Scylla.

At each end of the convoy’s passage, the escort was augmented by local escort forces from the UK to Iceland (seven destroyers including Campbell and five trawlers) and from Murmansk (four Soviet destroyers and three minesweepers).

Distant cover was provided by a 'heavy covering force' (the battleships Anson and Duke of York, the light cruiser Jamaica, and the destroyers Bramham, Keppel, Mackay and Montrose) under the command of Vice Admiral Sir Bruce Fraser), and a 'cruiser covering force' (the heavy cruisers London, Norfolk and Suffolk and their escorting destroyers) commanded by Vice Admiral S. S. Bonham-Carter.

At the same time the British sent two forces to Spitsbergen, a cruiser force with reinforcements for the garrison there and a replenishment group for the convoy (the heavy cruiser Cumberland, the light cruiser Sheffield, and the destroyers Amazon, Bulldog, Cowdray, Echo, Eclipse, Oakley, Venomous, Windsor and Worcester). These would also be available to support PQ.18.

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, this force comprising nine submarines including Tigris and Tribune.

In the early stages of its development, 'Doppelschlag' resembled 'Rösselsprung' (i) inasmuch as the forces involved were to wait at readiness in their bases until a convoy was detected by air reconnaissance or the 'Eispalast' patrol line of 12 U-boats stationed in the Norwegian Sea to give early warning of any convoys approach. Once the convoy had been detected, the German surface warships were to move forward to the Altafjord and there await the order to sortie and attack.

As noted above, the German fear of losing a battleship or battle-cruiser in an engagement with the Allied naval forces was so great that only Adolf Hitler could give permission for the start of the second stage, namely the planned sortie into the Barents Sea. Once out from their base, the surface warships were to divide into two battle groups for the double blow that gave the operation its name: one group was to engage and draw off any Allied heavy warships with the convoy, and the other was then to attack the convoy’s merchant ships without serious opposition. The German warships earmarked for the operation were the heavy cruiser (ex-pocket battleship) Admiral Scheer, the heavy cruiser Hipper, the light cruiser Köln, and the destroyers Friedrich Eckholdt, Richard Beitzen, Z-23, Z-27, Z-29 and Z-30. The other major German warships in Norway, the battleship Tirpitz and the heavy cruiser Lützow (ex-pocket battleship Deutschland), were unavailable as they had been under repair since the end of 'Rösselsprung' (i).

The PQ.18 convoy departed Iceland on 7 September and was sighted on 8 September by a long-range aeroplane and then again on 10 September by an 'Eispalast' U-boat. On 10 September the ships of 'Doppelschlag' departed Narvik to move north to the Altafjord. The ships were spotted by patrolling British submarines and one of these, Tigris, made an unsuccessful attack. The ships reached the Altafjord early on the following day.

From this point the operation’s senior officers, Vizeadmiral Oskar Kummetz in Admiral Scheer and Vizeadmiral Otto Ciliax ashore, pressed for permission for the ships to sortie, but Hitler’s insistence that no damage should befall the ships rendered their operational scope so limited that Grossadmiral Erich Raeder, the German navy’s commander-in-chief, cancelled the operation.

Thus the attack on the PQ.18 convoy was left to the air force and the U-boat arm.

On 12 September the destroyer Faulknor sank Kapitänleutnant Heino Bohmann’s U-88 near Bjørnøya. On 13 September Korvettenkapitän Rolf-Heinrich Hopman’s U-405 and Korvettenkapitän Hans-Joachim Horrer’s U-589 sank the 7,191-ton US freighter Oliver Ellsworth and 3,559-ton Soviet freighter Stalingrad. In the course of several attacks, bombers of Oberleutnant Erich Bloedorn’s Kampfgeschwader 30 and torpedo bombers of Major Werner Klümper’s I/KG 26 and Major G. Hielscher’s III/KG 26 sank the 5,432-ton US freighter Wacosta, 4,826-ton US freighter Oregonian, 4,885-ton Panamanian freighter Macbeth, 5,441-ton Panamanian freighter Africander, 6,209-ton British freighter Empire Stevenson, 7,044-ton British freighter Empire Beaumont (7,044 tons) and 3,124-ton Soviet freighter Sukhona. The 7,177-ton US freighter John Penn was also lost to air attack on the same day. On 13/14 September Hawker Sea Hurricane single-engined fighters from Avenger shot down five German aircraft, though four of the Sea Hurricane fighters were also lost.

During the night of 14/15 September Korvettenkapitän Karl Brandenburg’s U-457 torpedoed the 8,992-ton British tanker Atheltemplar, which later had to be abandoned. In the afternoon the I/KG 26 lost 12 aircraft and seven crews and the III/KG 26 eight aircraft and seven crews, but the 6,049-ton US freighter Mary Luckenbach exploded after being hit.

The destroyer Onslow, aided by Fairey Swordfish aircraft of No. 825 Squadron from Avenger, sank Horrer’s U-589.

Adverse weather on 16 September prevented further air activity, but on the following day the convoy was again located, although an attack by the KG 26 was broken off. Brandenburg’s U-457 was sunk by the destroyer Impulsive.

On 18 September there was another attack by aircraft of the KG 26 and KG 30 in poor visibility, but warplanes of the former unit suffered a number of torpedo failures. A Hurricane fighter launched from the 7,092-ton British CAM-ship Empire Morn shot down two Heinkel He 115 floatplanes.

The escorting warships had by now been joined by the Soviet destroyers Gremyashchy, Kuybyshev, Sokrushitelny and Uritsky as well as the British minesweepers Britomart, Halcyon, Hazard and Salamander, but the convoy nonetheless lost the 5,446-ton US freighter Kentucky, and the 6,458-ton Panamanian freighter Troubador suffered bomb damage so severe that she had to be beached in the Kola inlet, and was later broken up.

In all, PQ.18 lost three ships (totalling 19,742 tons) to U-boat attack and 10 ships (totalling 55,915 tons) to air attack.

Also at sea at this time were the Soviet submarines K-21, K-1, Shch-422, M-174, Shch-403 and Shch-404. On 13 September, off the Porsangerfjord, Shch-422 attacked but missed the patrol vessel V 6108, on 15 September the anti-submarine vessel UJ 1103 and on 22 September an entire convoy. On the same day, in the area to the south of Kiberg, Shch-404 attacked but missed the hospital ship Alexander von Humboldt.

The German surface ships therefore had little effect on the passage of the PQ.18 convoy, though the mere threat of 'Doppelschlag' had forced the Allies to make a heavy commitment in the form of notably strong close, covering and distant escort forces.

The next opportunity for an attack by German surface ships arrived late in December, when 'Regenbogen' (i), which was schemed along lines similar to those of 'Doppelschlag', was launched against the JW.51B convoy and led to the 'Battle of the Barents Sea'.