German submarine U-921

German submarine U-921 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II.

She was ordered on 6 June 1941, and was laid down on 15 October 1941 at Neptun Werft AG, Rostock, as yard number 508. She was launched on 3 April 1943 and commissioned under the command of Oberleutnant zur See Wolfgang Leu on 30 May 1943.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-921 had a displacement of 769 t when at the surface and 871 t while submerged. She had a total length of 67.10 m, a pressure hull length of 50.50 m, a beam of 6.20 m, a height of 9.60 m, and a draught of 4.74 m. The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2800 to 3200 PS for use while surfaced, two SSW GU 343/38-8 double-acting electric motors producing a total of 750 PS for use while submerged. She had two shafts and two 1.23 m propellers. The boat was capable of operating at depths of up to 230 m.

The submarine had a maximum surface speed of 17.7 kn and a maximum submerged speed of 7.6 kn. When submerged, the boat could operate for 80 nmi at 4 kn; when surfaced, she could travel 8500 nmi at 10 kn. U-921 was fitted with five 53.3 cm torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes or 26 TMA mines, one 8.8 cm SK C/35 naval gun, (220 rounds), one 3.7 cm Flak M42 and two twin 2 cm C/30 anti-aircraft guns. The boat had a complement of between 44 — 52 men.

Service history
On 24 May 1944, U-921 was spotted off Norway, en route to Narvik, by a Canadian Sunderland, DV990, of 422/R Squadron RCAF piloted by F/O G.E. Holley. U-921 had been searching for GS U-476 which had been attacked from the air earlier in the day and badly damaged. U-921 was able to hit the Sunderland on its attack run causing it to crash into the sea after dropping three depth charges, which resulted in no damage to U-921 but all the crewmen of the Sunderland were lost.

Shortly after this first attack U-921 was sighted by another Canadian Sunderland, DW111, of 423/S Squadron RCAF piloted by F/L R.H. Nesbitt. U-921 was able to avoid the five depth charges dropped by the Sunderland but strafing wounded the commander, Oberleutnant zur See Wolfgang Leu, and two other crewmen. As U-921 was diving, Leu was able to get both of the wounded crewmen below, but then closed the hatch to prevent her from sinking, sacrificing himself. U-921 sailed for Trondheim, arriving 26 May 1944, under command of her I. WO (1st Wachoffizier) Leutnant zur See Hans-Joachim Neumann.

On 24 September 1944, 20 days into her second war patrol, U-921 sent her last radio transmission from 74.75°N, 13.83333°W, west of Bear Island in the Norwegian Sea, in which she stated that, due to unspecified damage, she needed to return to port. U-921 was ordered to continue to operate against Convoy RA 60 and postpone her return. On 2 October 1944 she was listed as missing when, after the end of the convoy battle, she failed to return to Narvik.

Wolfpacks
U-921 took part in one wolfpack, namely:
 * Grimm (9 September — 2 October 1944)