The Type IX U-boats were German ocean-going submarines whose construction was initiated in 1938. Depending on the subtype, the Type IX units were 76.5 m to 87.6 m long, 6.5 m to 7.5 m wide, and their underwater displacement ranged from 1,150 tons to 1,800 tons. The maximum surface speed of Type IX U-boats ranged from 18 knots to 21 knots, and the maximum underwater speed was approximately 7 knots. The main armament was 6 533 mm torpedo tubes: 4 bow and 2 stern, with a total of 22-27 torpedoes carried on board the ship. The secondary armament consists of 1 105mm cannon, or 1 105mm cannon, 1 20mm AA cannon, and 1 37mm cannon in the IX B, IX D-1 and IX D-2 subtypes.