Operation Catechism
Operation Catechism was the British air raid of World War II that destroyed the German battleship Tirpitz. It was conducted on 12 November 1944 by 29 Royal Air Force heavy bombers which attacked the battleship at its anchorage near the Norwegian city of Tromsø. The ship capsized after being hit by at least two bombs and damaged by the explosions of others, killing between 940 and 1,204 members of the crew; the British suffered no casualties.
The attack ended a long-running series of air and naval operations against Tirpitz that sought to eliminate the threat she posed to Allied shipping. The battleship had been moved to the Tromsø area in October 1944 after being crippled on 15 September during Operation Paravane. This attack had been carried out by the RAF's elite Nos. 9 and 617 Squadrons, who unsuccessfully attempted to strike Tirpitz again at Tromsø on 29 October during Operation Obviate.
Operation Catechism re-used the plans for Operation Obviate, and was conducted by the same squadrons. The aircraft departed from bases in northern Scotland and, due to clear weather conditions, the Commonwealth airmen were able to accurately target and bomb the battleship. The bombers were unmolested by a unit of German fighter aircraft that failed to take off from nearby Tromsø in time. One bomber was significantly damaged by anti-aircraft artillery.
Tirpitz capsized within minutes of being hit. Rescuers picked up hundreds of her crew from the water, but few of those trapped within the hull were saved. Several German military personnel were convicted of dereliction of duty following the attack. The battleship's destruction was celebrated in Allied countries and Norway, and is commemorated by several memorials and displays in museums.
Background
From early 1942, Tirpitz posed a significant threat to the Allied convoys transporting supplies through the Norwegian Sea to the Soviet Union. Stationed in fjords on the Norwegian coast, the battleship was capable of overwhelming the close-escort forces assigned to the Arctic convoys or breaking out into the North Atlantic. To counter this threat, the Allies needed to keep a powerful force of warships with the British Home Fleet, and capital ships accompanied most convoys part of the way to the Soviet Union.Tirpitz was repeatedly attacked at her anchorages in Norway by Allied forces over several years. Royal Air Force heavy bombers made four unsuccessful raids on the battleship between January and April 1942 while she was stationed at Fættenfjord. From March 1943, Tirpitz was based at Kaafjord in the far north of Norway. During Operation Source on 22 September, she was severely damaged by explosives placed on her hull by Royal Navy personnel who had used midget submarines to penetrate Kaafjord. On 3 April 1944, aircraft flying from Royal Navy aircraft carriers attacked Tirpitz during Operation Tungsten and inflicted further damage. A series of subsequent aircraft carrier attacks were unsuccessful, including Operation Mascot on 17 July and Operation Goodwood which was conducted between 22 and 29 August 1944.
After the failure of Operation Goodwood, it was decided that further carrier attacks against Tirpitz would be fruitless due to the inadequacies of the Royal Navy's aircraft and their armament. Accordingly, responsibility for sinking Tirpitz was transferred to the RAF's Bomber Command. On 15 September 1944, the elite Nos. 9 and 617 Squadrons attacked the battleship at Kaafjord in what was designated Operation Paravane. This operation employed Avro Lancaster heavy bombers armed with Tallboy heavy bombs and "Johnnie Walker" mines. The Tallboy bomb weighed and had been developed to destroy heavily armoured targets. When dropped from a high altitude, the bomb could penetrate a battleship's deck armour before exploding within the vessel. Tirpitz was struck by a single Tallboy during the attack that caused extensive damage to her bow and rendered her unfit for combat.
As Tirpitz could not be repaired and Soviet forces were advancing towards Kaafjord, Grand Admiral Karl Dönitz, the commander of the Kriegsmarine, ordered that she be transferred to near the northern Norwegian city of Tromsø and used as an immobile battery to defend the area from attack. Dönitz hoped that this would also convince the Allies that Tirpitz continued to pose a threat. An anchorage was selected just off the coast of the island of Håkøya where it was believed the water was shallow enough to prevent the battleship from sinking if another attack was successful. Tirpitz arrived there on 16 October. The depth of water at the mooring was found to be greater than anticipated, leaving the battleship vulnerable to capsizing. Because of the space needed by Tirpitzs torpedo nets, it was not possible to move her closer to shore.
RAF and Royal Navy reconnaissance aircraft located Tirpitz at Tromsø on 18 October. As the Allied intelligence services had not been able to confirm that the battleship had been crippled, it was considered necessary to conduct further air raids against her. Nos. 9 and 617 Squadrons attacked Tirpitz on 29 October during Operation Obviate. As the Tromsø area was within range of RAF bases in northern Scotland if the Lancasters were modified, this attack was somewhat simpler to conduct than Operation Paravane. To extend their range, the Lancasters were fitted with extra fuel tanks and more powerful engines and their forward and mid-upper gun turrets and pilot's armour plate were removed. The reduction in armament left the Lancasters very vulnerable to German fighter aircraft, and they would have to fly without escort as no British fighters had the range needed to reach Tromsø.
During Operation Obviate, the bombers flew north over the Norwegian Sea, and met up over Torneträsk lake in Northern Sweden. This violated Sweden's neutrality, but allowed the bombers to approach Tromsø from the south-east. The Allies believed the Germans would not expect an attack from this direction. Despite clear weather for most of the flight, Tirpitz was covered by cloud shortly before the Lancasters reached the point where they were to release their Tallboy bombs. The cloud made it impossible to accurately target the battleship, and the 33 aircraft which bombed achieved no hits. Tirpitz was slightly damaged by a near miss. One of the Lancasters made a forced landing in Sweden after being damaged by anti-aircraft gunfire, and the remainder returned to base.
Preparations
British
Bomber Command remained determined to sink Tirpitz as soon as possible and preparations for another attack began shortly after Operation Obviate. A report issued by the Royal Navy's Naval Intelligence Division on 3 November judged that it remained necessary to attack Tirpitz in northern Norway. The report argued that the battleship could potentially be repaired and made fully operational if she was left unmolested and able to reach a major port. As it would be difficult to target the battleship during the period of near perpetual darkness in the northern winter, further attacks had to be made within the 23 days before this commenced. No. 5 Group RAF directed on 3 November that the next attack on Tirpitz was to take place on 5 November, and would re-use the plans developed for Operation Obviate. The raid was designated Operation Catechism.Two de Havilland Mosquito meteorological aircraft were stationed at RAF Sumburgh from 4 November, from where they conducted daily sorties to monitor weather conditions in the Tromsø area. On the same day, twenty No. 9 Squadron and nineteen No. 617 Squadron Lancasters were dispatched to airfields in northern Scotland in preparation for the operation. A gale warning was issued that night and the raid was cancelled as a result on the morning of 5 November. Both squadrons returned to their home bases during the day. The two squadrons deployed again to Scotland on 7 November, but soon returned to their bases when the attack was cancelled.
On 10 November, the Lancaster crews were briefed for another attack on Tirpitz. Both squadrons moved to northern Scotland on 11 November when meteorological reports indicated that there would be clear weather over Tromsø for up to two days. The aircraft were split between RAF Kinloss, RAF Lossiemouth and RAF Milltown.
German
Tirpitzs defences were improved after Operation Obviate. Additional anti-aircraft guns were emplaced in the Tromsø area and torpedo nets were laid around the battleship. These augmented the protection offered by the anti-aircraft ships Nymphe and Thetis and several anti-aircraft batteries on the shore. Dredging operations to reduce the water level below the battleship's hull began on 1 November. By 12 November these were half complete. The smoke generators that had previously protected Tirpitz at Kaafjord were still being installed at the time of Operation Catechism and were not yet operational. In their place, seven fishing boats fitted with smoke generators were positioned near the battleship; these were not capable of generating a smokescreen that could completely cover Tirpitz.The battleship's crew continued regular training exercises, and remained concerned about further air attacks. On 4 November Tirpitzs commanding officer Captain Wolf Junge departed. He was replaced by the executive officer, Captain Robert Weber. Weber believed that within three weeks the days would be short enough to prevent further air attacks. On 12 November around 1,700 men were on board Tirpitz.
A force of 38 fighters was transferred to Bardufoss after Operation Obviate to bolster the Tromsø region's air defences. These aircraft formed part of Jagdgeschwader 5, and were under the temporary command of Major Heinrich Ehrler. The unit had been evacuated from Kirkenes in the far northeastern region of Norway as Soviet forces advanced towards the town, and was disorganised at the time of Operation Catechism. Most of the pilots at Bardufoss were inexperienced and ill-trained, and the unit had not been properly briefed on Tirpitzs presence in the area. Ehrler arrived at Bardufoss on 9 November en route to Alta, and decided to remain there until the morning of 12 November to oversee an emergency training programme for the fighter pilots.