Mützelburg joined the Reichsmarine of the Weimar Republic on 1 April 1932 as member of "Crew 32" (the incoming class of 1932). After spending two years on minesweepers, in October 1939 he joined the U-boat arm.[1] He spent five months commanding the school boat U-10 from June to November 1940 as part of 21st U-boat Flotilla,[2] receiving his first combat experience aboard U-100 under Joachim Schepke. He commissioned U-203 into 1st U-boat Flotilla in February 1941. On his eight patrols in the Atlantic, the US east coast, and the Caribbean Sea, he sank 19 ships for a total of 81,961 gross register tons (GRT), and damaged three more (17,052 GRT).[1]
Mützelburg died on 11 September 1942 in a freak accident. He was swimming in the Atlantic south-west of the Azores, and dived from the conning tower, but struck the deck head-first when the U-boat suddenly lurched in the swell. The supply U-boatU-462 arrived the next day with a doctor on board, but too late, and Mützelburg was buried at sea on 12 September 1942.[1]
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Fellgiebel, Walther-Peer (2000) [1986]. Die Träger des Ritterkreuzes des Eisernen Kreuzes 1939–1945 — Die Inhaber der höchsten Auszeichnung des Zweiten Weltkrieges aller Wehrmachtteile [The Bearers of the Knight's Cross of the Iron Cross 1939–1945 — The Owners of the Highest Award of the Second World War of all Wehrmacht Branches] (in German). Friedberg, Germany: Podzun-Pallas. ISBN978-3-7909-0284-6.
Rohwer, Jürgen (1999). Axis submarine successes of World War Two: German, Italian, and Japanese submarine successes, 1939-1945. Greenhill Books. ISBN978-1557500298.
Scherzer, Veit (2007). Die Ritterkreuzträger 1939–1945 Die Inhaber des Ritterkreuzes des Eisernen Kreuzes 1939 von Heer, Luftwaffe, Kriegsmarine, Waffen-SS, Volkssturm sowie mit Deutschland verbündeter Streitkräfte nach den Unterlagen des Bundesarchives [The Knight's Cross Bearers 1939–1945 The Holders of the Knight's Cross of the Iron Cross 1939 by Army, Air Force, Navy, Waffen-SS, Volkssturm and Allied Forces with Germany According to the Documents of the Federal Archives] (in German). Jena, Germany: Scherzers Militaer-Verlag. ISBN978-3-938845-17-2.