|Ordered||10 Apr 1941|
|Laid down||20 Jan 1942||Danziger Werft AG, Danzig (werk 122)|
|Launched||24 Sep 1942|
|Commissioned||13 Jan 1943||Ltnt. Hans Kolbus|
|Successes||No ships sunk or damaged|
Sunk at 1200hrs on 29 April, 1944 in the Mediterranean near Toulon, France, in position 43.07N, 05.55E, by US bombs.
U-421 operated with the following Wolfpacks during its career:
Coronel (4 Dec 1943 - 8 Dec 1943)
Coronel 1 (8 Dec 1943 - 14 Dec 1943)
Coronel 2 (14 Dec 1943 - 17 Dec 1943)
Föhr (18 Dec 1943 - 23 Dec 1943)
Rügen 6 (23 Dec 1943 - 26 Dec 1943)
Hela (28 Dec 1943 - 1 Jan 1944)
Attacks on this boat
3 Jan 1944
00.16 hours, Bay of Biscay: the inbound boat was attacked with eight depth charges and gunfire from a Leigh Light-equipped British Liberator aircraft (224 Sqdn RAF/C, pilot F/O Ethan Allen). U-421 fought back with AA fire, then escaped by crash-diving, suffering only minor damage. (Sources: Franks/Zimmerman)
2 Mar 1944
03.09 hours, off Cape St. Vincent: U-421 was attacked by a British Wellington Mk XIV aircraft (179 Sqdn RAF, pilot S/L R.G. Knott). The aircraft had located U-421 by radar and then illuminated it by Leigh Light, but the nose turret guns jammed after firing only 40 rounds. AA fire then knocked out the starboard engine, causing the six depth charges to miss, and another AA hit in the bomb bay disabled the radar. The crew had to jettison all superfluous equipment, including the damaged radar, to keep flying on one engine, and reached base after three hours. (Sources: Franks/Zimmerman)
2 recorded attacks on this boat.
Men lost from U-boats
Unlike many other U-boats, which during their service lost men due to accidents and various other causes, U-421 did not suffer any casualties (we know of) until the time of her loss.