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.
The Type IX U-boats were created as a development and a significantly improved version of the Type I A U-boats. Their swimming range, artillery and torpedo armament have been significantly increased. Several subtypes of this class of ships were created in the course of serial production. Chronologically, the first was the Type IX. Later, the Type IX B was created, with a slightly increased range and reinforced anti-aircraft armament. Another type was the Type IX C and C-40, which were larger than their previous ones and their maximum operating range was again increased - to almost 25,000 km. Finally, the last variants were the subtypes IX D-1 and IX D-2, in which the maximum speed was increased to 21 knots on the surface and the torpedo reserve. During World War II, ships of this type operated primarily in the Atlantic, against Allied merchant shipping, but also they went to the Indian Ocean.