This was a British air attack on the German battleship Tirpitz in the Åsenfjord near Trondheim in German-occupied Norway (27/28 April 1942).
The undertaking was conceived in a period during which the Allied convoys to and from the Soviet ports of the northern USSR were under major threat from the powerful German surface forces based in Norway. As a result of his strained resources, Admiral Sir John Tovey, commander-in-chief of the Home Fleet, arranged that the PQ.12 outbound and QP.8 homebound convoys should sail on 1 March so that elements of the Home fleet could undertake the simultaneous protection of both. On 5 March a Focke-Wulf Fw 200 Condor long-range reconnaissance bomber spotted and reported the PQ.12 convoy in a position to the south-east of Jan Mayen island. On the following day Tirpitz, escorted by three destroyers, sortied to attack the convoy in 'Sportpalast'. The departure of the German warships was spotted and reported by the British submarine Seawolf, which was on station outside Trondheim. At time time Tovey was sailing as distant cover for the convoys in the battleship King George V accompanied by the fleet carrier Victorious, and was then joined by the battleship Duke of York and battle-cruiser Renown, which had sailed from Iceland.
The size and weight of this British support operation was dictated by the fact that the Germans had Tirpitz available in Norwegian waters. On receipt of the news of Tirpitz's emergence on 7 March, Tovey steered toward the converging convoys. The weather was very bad, so neither the British nor the Germans could undertake air reconnaissance. On this day the two convoys, the Home Fleet and Tirpitz were all within 80 miles (130 km) of each other. Unaware that the Home Fleet was searching for him, Vizeadmiral Otto Ciliax, the Befehlshaber der Schlachtschiffe, decided to turn for home on 8 March. Aided by 'Ultra' intelligence based on interceptions of German Enigma-encrypted naval signals, Tovey turned the Home Fleet toward Tirpitz's intended rendezvous with her destroyers off the Lofoten islands group, and on 9 March he was 200 miles (320 km) to the west of the German battleship and therefore able to close sufficiently to launch 12 Fairey Albacore torpedo bombers from Victorious. Tirpitz lofted a dense anti-aircraft barrage against the British naval airmen, who were inexperienced but determined, but all the torpedoes missed and two aircraft were lost. Tirpitz now put into Narvik.
The incident had repercussions on both sides. Prime Minister Winston Churchill wrote to Admiral Sir Dudley Pound, the First Sea Lord, demanding an explanation of why 'twelve of our machines managed to get no hits as compared with the extraordinary efficiency of the Japanese attack on Prince of Wales and Repulse!'. In reply, Pound pointed out that 'an attack by twelve aircraft is not normally expected to produce more than one or possibly two hits on a fast moving target with armament intact' and that most of the hits on the battleships which Churchill had sent to their loss in the Far East, had been made after they had been stopped. In Germany, Grossadmiral Erich Raeder, the commander-in-chief of the German navy, placed further restrictions on German surface operations: there were to be no sorties until air reconnaissance had fully determined the British strength. Raeder also persuaded Adolf Hitler to order a resumption of work on the German aircraft carrier Graf Zeppelin, though the ship, which had been launched as far back as 1938, was in fact never completed.
Tirpitz remained a potent threat to the Arctic convoys. The battleship was well protected in her berth in the Åsenfjord by natural features and anti-torpedo booms. Moreover, British intelligence believed that there were more than 100 German fighters in the area, which possessed a radar control system. Thus an attack by day stood no chance of success, and the problems of navigation at night were also great.
The commander-in-chief of RAF Coastal Command, Air Chief Marshal Sir Philip Joubert de la Ferté, thought that low-flying Bristol Beaufort torpedo bombers of his command might be able 'to damage technical equipment with high explosive hits on the upper deck'.
Inevitably, therefore, Air Marshal A. T. Harris’s RAF Bomber Command, which at least had some chance of causing major damage, was entrusted with the task of bombing Tirpitz once again. A force of 33 Handley Page Halifax heavy bombers attacked Tirpitz at Trondheim on the night of 30/31 March: few of the bombers managed to locate their target, none hit the German battleship, and five aircraft were lost.
RAF Bomber Command tried once again in April. The command was deep in the process of learning from painful experience, and the complexity of this 'Bluebeard', which was undertaken by aircraft of Nos 4 and 5 Groups, illustrates the lengths to which Bomber Command was prepared to go in order to defeat Tirpitz's defences. The operation was planned in two phases: in the first, one squadron of Halifax bombers and two squadrons of Avro Lancaster heavy bombers carrying 4,000-lb (1814-kg) bombs were to attack the ship’s anti-aircraft defences; and in the second, two squadrons of Halifax bombers were to roll 1,000-lb (454-kg) spherical mines, fitted with carefully calculated depth fuses, under the target to detonate below the hull. This latter phase would have been extraordinarily difficult to execute under perfect conditions and without opposition, and was now to be undertaken at night and against a skilled and determined opponent.
It was hoped that a series of diversions by Coastal Command would confuse the German radar. Two Lockheed Hudson long-range maritime patrol aircraft were to loiter off Kristiansund, as would a Consolidated Catalina flying boat off Stokken island to distract the German radar. Another 10 Hudson aircraft were to attack shipping at Ålesund and Bristol Beaufighter heavy fighters were to strafe the airfields of Lade, Vaernes and Herdla.
On 23 April the aircraft involved moved north to their advanced bases in Scotland. The crews were briefed two days, but the operation was then postponed as a result of poor weather. 'Bluebeard' was this launched on 27 April. On the whole, the Coastal Command part of the plan was successful. The 31 Halifax and 12 Lancaster bombers were spotted and engaged 100 miles (160 km) from the target at Smolen island, and in theory the German radar should have detected them up to 35 miles (55 km) farther to the west of that point. Yet Tirpitz's defensive smoke screen started only five minutes after the first bomber had arrived, and was not effective until some 25 minutes into the raid. The British crews later noted, however, that the smoke screen, about which they had not been briefed, was a key reason why they missed the target. The bombers were met by extremely heavy Flak, and lost one Lancaster and four Halifax bombers.
Coastal Command lost one Beaufighter as it strafed Lade. The Catalina, its lights illuminated, loitered over Stokken but provoked no response. There were no hits on Tirpitz, and the Germans found the mines littering the side of the fjord stuck behind trees and rocks.
Bomber Command attacked once again on the following night with 23 Halifax and 11 Lancaster bombers, found the ship fully concealed by smoke, and lost another two Halifax aircraft. Once more there were no hits, and it was clear that air attack at extreme range was proving both costly and ineffective. The impetus then returned to the Royal Navy, which received many concepts and investigated several of them, and it was this which paved the way for later attacks by human torpedoes, submersible boats and midget submarines.