Erhard Maertens or Eberhard Maertens (26 February 1891 – 5 May 1945) was a German Vizeadmiral of the Kriegsmarine during World War II. From 16 June 1941 to 5 May 1943, he was Chief of Office of Naval Intelligence, Naval War Command () in the Oberkommando der Marine. Maertens was known for underestimating British intelligence, and specifically, overrating the security of the Naval Enigma cipher machine. In 1941, he held a naval enquiry into the strength of Naval Enigma security after the capture of U-boat U-570, and attributed all the suspicious losses in U-boats at the time to the British Huff-Duff. In the second enquiry, ordered by the Commander-in-Chief of the Navy () Karl Dönitz, in May 1943, he investigated a number of areas, which exculpated Enigma security in the end, for the second time, incorrectly blaming British 9.7 centimetre centimetric radar for the massive losses in U-boats by mid 1943.
Naval career
On 1 April 1910, Maertens joined the Imperial German Navy as a Seekadett and had basic training on the heavy cruiser until 31 March 1911. He was promoted to an officer candidate rank () and sent to the German Imperial Naval Academy Naval Academy Mürwik for Naval training until 30 September 1912. In September 1913, he was promoted to Midshipman () after completing his training.
From 1 October 1912 to 7 October 1915, Maertens was posted to the liner Hessen to learn the sailing characteristics of large ships and their movements. On 8 September, Maertens started submarine and radio training, and later posted as a watch officer on the U-boat U-3 on 17 October 1915. He completed his submarine training on 26 February 1916, promoted on 22 March 1916 to Oberleutnant zur See, and was posted to U-boat U-47 as the watch officer the day after. He was subsequently posted to U-48, to take up the same post, until 24 November 1917, when U-48 ran aground on Goodwin Sands, where the submarine was fired on by and was scuttled and abandoned. Maertens and 17 other submariners of U-48 were taken as prisoners, and held in captivity until 5 November 1919.
After being released, Maertens was subordinated to the battleship for a month as a watch officer. In early 1920, he was posted to Baltiysk for two months as a Naval Signals Officer. On 1 January 1921, he was promoted to captain lieutenant, (), an officer grade of the captains military hierarchy group. On 1 March 1921, Maertens was ordered to be acting leader of the service office at Königsberg. On 7 April 1921, he was subordinated as Adjutant and Naval Signals Officer to the Commander of the naval base at Świnoujście. In October 1921, he was posted to the Coastal Defence Battalion I as company leader where he stayed until March 1925.
On 1 January 1921, Maertens was promoted to captain lieutenant (). On 17 March 1925, he was subordinated to the commander of the Torpedo and Mining Academy in Kiel where he stayed until 14 August 1928. From 15 August 1928 to 30 September 1934, he was the department head of the Naval Shipyard of the Naval Command (). In October 1934, Maertens was promoted to Frigate captain, (), which was the senior middle rank of the Kriegsmarine. From 1934 to 1936, he was Commander of the Naval Academy Mürwik. He was then posted to the Bureau of Inspection of the torpedo Service in Kiel as Director of Staff until 30 September 1937. During the same period he was ordered to be Acting Inspector of Torpedo Affairs until 17 April 1937. From October 1937 to April 1939, Maertens was Director of Staff of Inspections in Naval Signals and, order again, on a temporary basis, to be Acting Inspector of Naval Signals from May 1938 to March 1939. He then became leader and subsequent Commander of the Communication Test Institute of the OKM from 28 April 1939 to 18 November 1939. He was again promoted to Director of the Technical Signals Affairs in the Naval Weapons Office in the Oberkommando der Marine from 19 November 1939 to 15 June 1941. On 1 July 1940, Maertens was promoted to rear admiral, Konteradmiral, and on 1 September 1942, promoted to Vizeadmiral. From 19 June 1941 to 5 May 1943, he was promoted to Group Director of the Naval Intelligence Service, ( III) of the Oberkommando der Marine (OKM/4 SKL III). From 6 May 1943 to June 1943 Maertens was Acting Shipyard Director of the Kriegsmarine shipyard in Kiel. From 28 November 1944 to 28 February 1945, he was placed at the disposal of Oskar Kummetz who was the Baltic Sea regional commander.
Maertens retired on 28 February 1945.