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Naval Warfare

Type XXIII U-Boat

Coastal Attack Submarine [ 1944 ]

The compact German Type XXIII coastal submarine appeared in some 61 total operational examples before the end of World War 2.

Authored By: Staff Writer | Last Edited: 01/09/2018 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

The Kriegsmarine Type XXIII were developed as smallish coastal submarines to operate in the shallow waters between England and France and the Mediterranean Sea. These boats were part of the all-new electric boat designs pioneered by the Germans in the latter stages of the war. These vessels were purposely designed to operate almost exclusively underwater without a detrimental need to surface. This was accomplished through the extensive use of high capacity battery cells and a snorkel to feed air to the diesel engines when the craft was submerged. The Type XXIII was developed alongside the larger Type XXI electric boats and intended to operate where the bigger Type XXI could not.

Small by design, the Type XXIII was fielded with a crew of 14 to 18 personnel and only two torpedoes. Sharing development with the Type XXI, the two systems had commonality in parts and operating philosophy. 2 x bow-facing 21" (533mm) torpedo tubes were a required part of the design and no surface deck gun was included. The Type XXIII was in design by 1942 and in construction by 1943, with the first launching in 1944. Another similarity to the XXI was that the XXIII was constructed as major sections(four for the XXIII while eight for the XXI) at separate locations only to be assembled altogether at a main yard.

Propulsion was derived from a diesel engine (when surfaced) and two electric motors (when submerged). The diesel unit consisted of an MWM brand RS134S type 6-cylinder engine developing roughly 575 horsepower. When submerged, the submarine could call upon its AEG GU4463-8 double-acting electric motor (generating up to 572 horsepower) for full undersea flight. When quietness was a requirement, the crew could elect to switch on its BBC CCR188 electric creeping motor, a system generating 35 horsepower at the cost of silence. The vessel exhibited a top surface speed of 9.7 knots but increased that when submerged to an impressive 12.5 knots. Depths of up to 590 feet were possible. Surface ranges centered on about 1,500 miles while this was curtailed heavily when submerged - limited to just 202 miles at 4 knots.©MilitaryFactory.com
Once in the water, the Type XXIII proved to be of sound design and exhibited responsive handling in all quarters of submarine activity. A low reserve buoyancy and lack of most of its outer casing meant that the system could submerge itself in a matter of seconds, as fast as 9 or 10 seconds according to some sources. Its size, power and limited operating depth forced the craft to attack targets within close range. Conversely, its size and operational abilities allowed the vessel to utilize stealth practices to ensure it was unseen before firing its payload.

The Type XXIII operated through to the end of the Second World War to which just seven total units were lost and these to air attacks. Only three survived in the post-war months while the rest were either sunk by controlled Allied fire after capture or scuttled by their German crews. Construction was handled by Deustche Werft at Hamburg and Germaniawerft at Kiel. 48 boats were constructed at Hamburg alone. Though 280 were initially ordered, a fraction of these were constructed and eventually entered active service with only a few actually seeing combat action.©MilitaryFactory.com
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Nazi Germany
Operators National flag of modern Germany National flag of Nazi Germany
Nazi Germany
National Origin
Type XXIII U-Boat
Hull Class
U-2321; U-2322; U-2323; U-2324; U-2325; U-2326; U-2327; U-2328; U-2329; U-2330; U-2331; U-2332; U-2333; U-2334; U-2335; U-2336; U-2337; U-2338; U-2339; U-2340; U-2341; U-2342; U-2343; U-2344; U-2345; U-2346; U-2347; U-2348; U-2349; U-2350; U-2351; U-2352; U-2353; U-2354; U-2355; U-2356; U-2357; U-2358; U-2359; U-2360; U-2361; U-2362; U-2363; U-2364; U-2365; U-2366; U-2367; U-2368; U-2369; U-2371; U-4701; U-4702; U-4703; U-4704; U-4705; U-4706; U-4707; U-4709; U-4710; U-4711; U-4712

Submerged Attack
Traveling under the surface to search, track, and / or engage or reconnoiter areas.
Maritime Patrol
Active patroling of vital waterways and maritime areas; can also serve as local deterrence against airborne and seaborne threats.
Fleet Support
Serving in support (either firepower or material) of the main surface fleet in Blue Water environments.

112.0 feet
(34.14 meters)
9.9 feet
(3.02 meters)
12.2 feet
(3.72 meters)
Displacement (Submerged)

1 x MWM RS134S 6-cylinder diesel engine developing 575 horsepower; 1 x AEG GU4463-8 double-acting electric motor generating 572 horsepower; 1 x BBC CCR188 electric creeping motor generating 35 horsepower; 1 x shaft.
10.0 knots
(11.5 mph)
Surface Speed
12.0 knots
(13.8 mph)
Submerged Speed
1,351 nm
(1,555 miles | 2,503 km)
1 knot = 1.15 mph; 1 nm = 1.15 mile; 1 nm = 1.85 km

2 x 21" (533mm) torpedo tubes (bow facing; 2 total torpedoes)


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