Günther Hessler joined the Reichsmarine of the Weimar Republic on 5 April 1927 as a member of "Crew 1927". He underwent basic military training in the 8th company, 2nd department of the standing ship division of the Baltic Sea in Stralsund. Hessler was then transferred to the training ship SSS Niobe, attaining the rank of Seekadett on 1 October 1927. After more than 16 months aboard the light cruiser he underwent officer cadet training at the Naval Academy at Mürwik, which included navigational training cruises on the tender Frauenlob and the survey vessel Meteor. Hessler then advanced in rank to Fähnrich zur See on 1 April 1929. On 2 October 1936 he was appointed watch officer on the AvisoGrille, Adolf Hitler's state yacht, and on 30 March 1938 transferred to the battleship Gneisenau. In 1937 he married Karl Dönitz's daughter, Ursula. The marriage produced two sons, Peter and Klaus, and a daughter, Ute. Hessler took command of torpedo-boat Falke on 27 March 1938. He remained in this position until 8 January 1940, earning the Iron Cross 2nd Class on 18 November 1939. Falke was assigned to the 5th Torpedo-boat flotilla on 4 April 1939. On the outbreak of World War II Falke was tasked with laying defensive naval mines and escort and security duties in the North Sea. In April 1940 Hessler transferred to the U-boat arm, and six months later commissioned the, without, unusually, having served as either a 1. Wachoffizier or a Kommandantenschüler. On his first patrol Hessler sank four ships with a total of, but he became famous on his second patrol — the most successful patrol of the entire war — sinking 14 ships with a total of. Oberleutnant zur SeeHelmut Witte was his first watch officer on these two patrols. His third patrol accounted for another three ships, totalling 13,641 tons, giving Hessler a career tally of 21 ships totalling, including two Royal Navy ocean boarding vessels HMS Crispin and. Hessler then handed over command of U-107 to Harald Gelhaus and transferred to the Befehlshaber der U-Boote. He served on the naval staff as 1. Admiralstabsoffizier from 24 November 1941 until the end of the war in Europe on 8 May 1945.
Post-war
After the war Hessler spent over a year in Allied captivity, and testified at the Nuremberg Trials on behalf of the Ubootwaffe and his father-in-law, Großadmiral Karl Dönitz. In 1947 Hessler was commissioned to write The U-Boat War in the Atlantic, a definitive account of the German U-boat offensive, by the British Royal Navy. Assisted by Alfred Hoschatt, the former commander of U-378 and also a staff officer of the BdU, he completed the three volume work in 1951. Hessler died in 1968 aged 58.
Summary of career
Ships attacked
As commander of Günther Hessler is credited with the sinking of 19 merchant ships with a total of and two auxiliary warships of.
