at low level, releasing the stored water. 15 October 1944 – Sorpe dam Target of the original Dambusters raid survived a second attack by 9 Squadron (617 Squadron did not participate in this raid). The Tallboy bombs were seen to hit the dam but did not breach it. Raids on Tirpitz The German battleship Tirpitz was a threat against convoys sailing to and from the Soviet Union. 15 September 1944 – (Operation Paravane) One Tallboy hit near the bow of the Tirpitz, passing through the foredeck and hull, and exploded in the water on the starboard side of her bow. The blast wrecked the bow, and left the battleship's forward compartments flooded with 2,000 tons of water. The explosions of several other Tallboys in the water near Tirpitz also buckled some of her hull plates and bulkheads. Five men were killed and fifteen wounded. Tirpitz was rendered unseaworthy and the damage was assessed as needing nine months' worth of work to repair, but this was considered unfeasible so the battleship was relegated to a floating artillery battery. 29 October 1944 – (Operation Obviate) Due to cloud coming in just before the attack, 32 bombs were dropped "blind". No direct hits were scored but one near miss bent a propeller shaft. 12 November 1944 – (Operation Catechism) In the final operation the Tirpitz was sunk by three Tallboys hits, and several others fell close by. Several bombs landed within the anti-torpedo net barrier and caused significant cratering of the seabed, removing much of the sandbank that had been constructed to prevent the ship from capsizing. One bomb penetrated the ship's deck between turrets Anton and Bruno but failed to explode. A second hit amidships between the aircraft catapult and the funnel, completely destroying the entire section of belt armour abreast of the bomb hit and blowing a very large hole in the ship's side and bottom, causing significant flooding and a port list to 60 degrees. A third bomb struck the ship on the port side of turret Caesar, eventually leading to a magazine explosion that caused the ship to capsize. December 1944 – April 1945 Bombing of U-boat pens, December 1944 – April 1945 15 December 1944 – IJmuiden on the Dutch coast, 617 Squadron attacked E-boat pens with Tallboys. A smoke-screen hindered the bombing, and the results went unseen. 12 January 1945 – Bergen 32 Lancasters and one Mosquito