Type IXA U-boats ranged from U-37 to U-44. Armament was six torpedo tubes, 1 x 10.5cm deck gun, 1 x 3.7cm Flak gun and 1 x 2cm Flak gun. Her 22 torpedoes could be replaced with 66 mines. From 1943 to 1944, the 10.5cm deck was often omitted and replaced with an additional Flak gun. Of the eight vessels put to sea, six were sunk from 1939 to 1943 while two were scuttled in May of 1945 (U-37 and U-38).
As the Type IXA series was earning its run on the waters, the Type IXB was already being developed. This series encompassed some 14 total boats ranging from U-64 and U-65, U-103 to U-111 and U-122 to U-124 with service running from 1939 to 1940. These submarines were also produced by AG Weser at the Bremen shipyard. Essentially, the Type IXB was an improved class of boat that sought to further improve the operational ranges inherent to the Type IXA design. By the end of it all, the Type IXB group would prove the most successful of all the Type IX series and leave many-a-U-Boat ace to her legacy. The 22 onboard torpedoes could be replaced with 66 mines. Nearly all Type IXB boats could account for an average of 100,000 tons of goods sunk by the war's end. All Type IXB systems were lost with the exception of U-123, her being decommissioned on June 17th, 1944 at Lorient.
The Type IXC was introduced into the series line and quickly became the largest operating group of Type IXC boats. Construction was yet again handled by AG Weser and 54 of its type were produced during the war. The Type IXC was fitted with additional internal fuel stores to further improve the submarine's range. Type IXCs could also be fitted as minelayers and make use of 66 TMB or 44 TMA series mines though most were usually not fitted as such. This group encompassed U-66 through U-68, U-126 through U-131, U-153 through U-166, U-171 through U-176 and U-501 through U-533.
The Type IXC was little bettered in the Type IXC/40 group. These boats were given improved ranges and surface speeds and numbered 87 in total. Construction was handled by AG Weser, Deutsche Werft (Hamburg) and Seebeckwerft (Bremen). There U-boats were U-167 to U-170, U-183 to U-550, U-801 to U-806, U-841 to U-846, U-853 to U-858, U-865 to U-889 and U-1221 to U-1235.
Most all Type IXCs were sunk by the end of the war. Service for the Type IXC ran from 1941 to 1942 while the Type IXC/40 was commissioned from 1942 to 1944.
With development beginning as early as 1940, the Type IXD was put to sea by 1942. These boats were given an extra 35.4 feet of hull length for which to work with. Three subvariants made up the Type IX variant itself and were designated as the IXD1, IXD2 and the IXD2/42.
Two Type IXD1 examples were delivered (U-180 and U-195), but these lacked any viable armament (no torpedoes, just the deck gun and seven Flak cannons), used instead as ocean-going refueling vessels for other U-boats in operation. Type IXD1s could haul some 250 tons of fuel and were faulted for their inconsistent experimental diesel engines - the latter implementation was not used in further Type IXDs that were to follow. The engines were 6 x 20-cylinder, four-stroke Mercedes-Benz MB501 "Vee" diesel systems generating an impressive 9,000 horsepower. These were later replaced by a pair of 6-cylinder, four-stroke Germaniawerft F46 super-charged diesel engines. Submerged power came from 2 x SSW GU345/54 double-acting motors generating 740kW. U-180 was lost west of Bordeaux on August 24th, 1944 and U-195 was taken over by the Japanese on May 6th, 1945.
The Type IXD2 comprised of 28 boats and made up the larger part of the Type IXD class as a whole. These put forth ever increasing operational ranges topping off at an impressive 36,290 miles. Type IXD2s were able to reach operations as far away as Japan and the Indian Ocean, making it one of the more lethal U-Boat systems to date. The torpedo count increased to 24 (or 72 mines in their place). Operations ran from 1942 to 1944 with most sunk before the end of the war.
The Type IXD2/42 was nearly identical to the preceding Type IXD2s but were given improved engines with greater output - approximately 1,000 more horsepower than in the original Type IXD2s. Only two IXD2/42 systems were reportedly made available for service. U-884 was damaged by Allied bombs while still in the dockyard on March 30th, 1945. U-883 surrendered on June 21st, 1945 at Wilhelmshaven.
Type IXD submarines were made up of the U-177 to U-182, U-195 to U-200, U-847 to U-852, U-859 to U-864 and U-871 to U-876. U-883 and U-884 were the only two IXD2/42 completed. U-885, U-886, U-887 and U-888 had begun construction but their progress was cancelled in whole on September 30th, 1943 when the IXD2/42 contract was itself cancelled. From 1943 to 1944, the torpedo tubes were removed from many of the Type IXDs in circulation.
U-505, a Type IXC U-Boat can be seen in all her glory at the Museum of Science and Industry in Chicago, Illinois, USA. She was fully restored in 2005. The only other Type ICX preserved is the U-534, available for viewing in Birkenhead, England, UK.
The Type IX was eventually succeeded by the Type X class U-Boat.