Operation Obviate

Tirpitz

Date	29 October 1944
Location	Tromsø, Norway 69°40′N 18°57′E / 69.667°N 18.950°E / 69.667; 18.950
Result	Minor damage, no direct hits

Belligerents

RAF Bomber Command

Kriegsmarine

Commanders and leaders

Group Captain "Willie" Tait

KzS Wolf Junge

Strength

37 Avro Lancasters

Tirpitz (Bismarck-class battleship)

Operation Obviate was the RAF Bomber Command attack on the German battleship Tirpitz at Tromsø on 29 October 1944. The attack was foiled by cloud covering the ship at the last minute, and the bombs that were dropped caused only minor damage. Tirpitz would finally be sunk in Operation Catechism two weeks later.

Tirpitz was a Bismarck-class battleship of 42,900 tons, armed with eight 38 cm (15 inch) guns. She was designed to attack merchant shipping in the Atlantic, but the loss of Bismarck and other commerce raiders led to instructions that she should be used for limited sorties only. In early 1942, Tirpitz was sent to northern Norway, where she would remain for most of World War II. She acted mainly as a fleet in being, threatening the Arctic convoys and tying up three British battleships that were needed elsewhere.

Tirpitz had been damaged in Kåfjord by a raid (Operation Paravane) on 15 September 1944 by No. 617 Squadron and No. 9 Squadron RAF from a base in the Soviet Union. The Germans decided that the ship could not be repaired and towed her 200 miles south, for use as a static battery in the defence of Tromsø against an expected Allied invasion. The British were unaware of the damage and so continued plans to sink Tirpitz. However the move to Tromsø had brought her within range of aircraft flying from British airfields such as RAF Lossiemouth.

When news came of Tirpitz's move to Tromsø, Air Vice Marshal Ralph Cochrane of No. 5 Group RAF made plans for an attack using Tallboy bombs dropped from high altitude to penetrate the battleship's armour. However Tromsø was at the limits of the range of an Avro Lancaster bomber carrying a Tallboy. The planes needed an extra 300 gallons of fuel, but the Tallboy prevented the use of extra fuel tanks in the bomb bays. Cochrane's engineering staff officer, Wing Commander Brown, came up with the idea of using long, thin tanks from the Wellington inside the fuselage of the Lancasters. This gave them a fuel capacity of 2,406 gallons, just enough for the 2,250 mile trip, but it left the aircraft 2 tons overweight, even after the mid-upper turret and some of the armour was removed. So "Willie" Tait requisitioned more powerful Merlin 24 engines from other Lancasters in 5 Group, and had them fitted into the aircraft of 617 and 9 Squadrons, which had specially modified bomb bays to carry the Tallboy. Then they had to wait for a break in the weather. Since the aircraft were required to be on standby for emergency tasks in France, they were only sent up to Lossiemouth from their bases in Lincolnshire when the weather looked like clearing.

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Wikipedia