Erhard Maertens

Erhard Maertens or Eberhard Maertens (26 February 1891 in Głogów – 5 May 1945 in Berlin) was a German Vizeadmiral of the Kriegsmarine during World War II. Between 16 June 1941 and 5 May 1943, Maertens was Chief of Office of Naval Intelligence, Naval War Command (Marinekommandoamt) in the Oberkommando der Marine. Maertens was principally known for permanently underrating British Intelligence, and specifically in overrating the security of the Naval Enigma cipher machine. In 1941, Maertens held an 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. The second enquiry, ordered by Commander-in-Chief of the Navy (Oberbefehlshaber der Kriegsmarine) Karl Dönitz, in May 1943, he investigated a number of areas, but finally exculpated Enigma security, for the second time, incorrectly blaming British 9.7 centimetre Centimetric radar, for the massive losses in U-boats, by mid 1943.

Naval career
In 1 April 1910 Maertens joined the Imperial German Navy as a Seekadett and undertook Basic Training on the heavy cruiser SMS Hansa (1898) until 31 March 1911. He was promoted to an Officer candidate rank (Fähnrich zur See) 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, (Leutnant zur See) upon completion of his training.

Between 1 October 1912 and 7 October 1915, he 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 she was fired on by HMS Gipsy (1897) and finally scuttled and abandoned. Maertens was taken prisoner, along with 17 other submariners of U-48 and held in captivity until 5 November 1919.

After being released, Maertens was subordinated to the battleship SMS Schwaben, for a month, as a watch officer, and rapidly moved up in his postings. He was later posted to Baltiysk in early 1920 for two months, as a Naval Signals Officer. On 1 January 1921, he was promoted to Captain lieutenant, (Kapitanleutnant), an officer grade of the captains military hierarchy group. On 1 March 1921, Maertens was ordered to Königsberg to take up a position as acting leader of the service office. 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 (Kapitanleutnant). On 17 March 1925, he was subordinated to the commander of the Torpedo and Mining Academy in Kiel, where he remained until 14 August 1928. Between 15 August 1928 and 30 September 1934, he was department head of the Naval Shipyard of the Naval Command (Reichsmarine). In October 1934, Maertens was promoted to Frigate captain, (Fregattenkapitän), which was the senior middle rank of the Kriegsmarine. Between autumn 1934 and autumn 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, on a temporary basis. Between October 1937 and 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 between May 1938 to March 1939. He then became leader and subsequent Commander of the Communication Test Institute of the OKM between 28 April 1939 and 18 November 1939. He was again promoted to Director of the Technical Signals Affairs in the Naval Weapons Office in the Oberkommando der Marine between 19 Nov 1939 and 15 Jun 1941. On 1 July 1940, Maertens was promoted to Rear Admiral, Konteradmiral and promoted to Vizeadmiral in 1 September 1942. Between 19 June 1941 and 5 May 1943, he was promoted to Group Director of the Naval Intelligence Service, (Seekriegsleitung) 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.

Enigma Security Enquiries
Maertens was a career navy signals officer, who was promoted to the Director of the Naval Intelligence Command (Marinenachrichtendienst), in June 1941, at a time when the B-Dienst, the Naval Intelligence department of the Kriegsmarine, was in a period when it was at its most active.

In May 1941, Captain Ludwig Stummel, a Nazi, who was Group Director of Naval Warfare department, was a subordinate of Maertens. After the sinking of 8 destroyers and the U-boat, U-13 in April–May 1940, Stummel started a probe, into the sinking. Vice admiral Karl Dönitz requested confirmation that the sinking of the submarine had effected the change in movement of a convoy that was being targeted and was specifically asking for assurances of Enigma M's security. Konteradmiral Erhard Maertens, coming to the aid of his subordinate, stated that four events would need to occur, which would make it highly unlikely:


 * 1) That U-boat submariners being threatened capture or destruction, had not destroyed the Enigma machinery or changed the configuration.
 * 2) That water-soluble ink would not work.
 * 3) That the enemy could detect the difference between the settings and those of the key list.
 * 4) That the British Admiralty could solve B-Dienst messages and extract the correct intelligence to enable the convoy to avoid the U-boats.

Maertens believed these events taken singly were unlikely and together impossible. In an attempt to ensure the U-13 and all associated Key M, i.e.Enigma cipher machine infrastructure was destroyed, a bombing raid was ordered. The crew of one of the planes noticed that the site of the U-13 was marked by buoys, indicating perhaps, the submarine had not been salvaged. This was stated in the official report. In that case, the British Admiralty had not recovered any Key M material or machinery.

1941 Investigation
Maertens was requested [ordered] to lead a formal enquiry into the control and investigation of own processes, when the capture of U-boat U-570 in August 1941, later renamed to HMS Graph by the Admiralty occurred, potentially leaking German secure communication details, i.e. Key M secrets to the British Admiralty. This was considered by Naval Intelligence to be a progression and continuation of previous investigations and probes, a process which had been in place since the Naval Enigma cipher machine was first introduced. One of these investigations had been conducted by Kurt Fricke, Chief of Naval War Command, on another incident, the sinking of the German battleship Bismarck on 27 May 1941 caused great consternation in the Kriegsmarine, that had resulted in a number of changes to Enigma cipher processes. On 18 October 1941, Maertens completed his analysis of the security consequences by stating in his report that:


 * a current reading of our messages is not possible

On the next page, however, he conceded that if the enemy had found the Enigma cipher machine undisturbed with all the key documents, a current reading was possible. Because of their long voyages, U-boats routinely carried two to three months worth of daily key settings, so in the enemy could have used U-570's material to read enciphered messages until November 1941. If these documents had fallen into enemy hands, the results Maertens conceded, would be


 * without doubt a weakening of the security of our cipher

But he concluded that this was unlikely, that there was time to drench the documents, making their water-soluble ink unreadable. And in the end, he left the impression that the British were not solving Enigma messages. In fact, once captured, a search of U-570 was conducted and useful papers had missed destruction, by the departed German crew. Copies of encrypted signals and their corresponding, plain-language German texts were in fact found by the British. The U-570 papers included all the supporting documentation for the Naval Key M ciphers.

Maertens verdict in his final report had some very worrying conclusions:


 * We have to accept that the U-570 might have been captured by the enemy without anything having been destroyed. In these circumstances it cannot be rules out that... a large amount of cipher documents are in enemy's hands. If this is true, the security of our enciphering procedure has been weakened... Out cipher will have been compromised if, as well as the enemy capturing the codebooks, our officers, who are now POW's have told the enemy the keyword, which since June 1941 has been given verbally to the U-boat commander so that he could alter the printed list of Enigma settings. If that has occurred, then we have to accept that our radio messages are being read by the enemy...The same would be true if the keyword had been written down in breach of regulations, and the codebooks and the keyword had fallen into enemy hands, or if, for example, the settings arrived at by the keyword order were written on the original settings list. If this happened, the enemy could work out the meaning of the keyword.

1941 Tarafal Bay Action
In another incident, the action in Tarrafal Bay, worried Donitz and another investigation was launched by Maertens. Maertens noted that the U-boat U-111 had detailed a meeting point in a message transmitted on 23 September 1941, four days before the ambush. Maertens stated that:


 * if U-111 message was read, then there would be an attempt to disturb the meeting.

However, he again shied away from directly suggesting that Key M infrastructure had been compromised. He could not believe that the British could not make such a mess of the attack in such favourable conditions if the Naval Enigma cipher had been broken. On 24 October 1941, Maertens overall conclusion was stated in a letter to Donitz:


 * The acute disquiet about the compromise of our Secret Operation cannot be justified. Our cipher does not appear to be broken.

In fact, the Naval Intelligence Division had solved a message intercepted from U-111, and the Admiralty had dispatched the submarine HMS Clyde (N12) to destroy the U-boats in the Bay of Tarrafal on the island of Santo Antão.

1943 Investigation
In February and March 1943, Admiral Dönitz met with Adolf Hitler 4 times to discuss the Battle of the Atlantic, and the point that the Allies seemed to know the location of U-boat groups as they were routing the convoys around the U-boat packs, and it was strongly suspected that the Allies had broken the cipher machine, and again Maertens was asked to conduct another enquiry. Maertens again assured Donitz and exculpated the Enigma cipher machine security. Around the same time, documents had been found in French Resistance agent's station showing that the Allies were obtaining information from the Resistance on departure times for U-boats and whether the U-boats were heading north or south, enabling the foe, Maertens thought to estimate submarine movements with some accuracy. Maertens was supported in his assumptions by the discovery of Centimetric Radar, on a downed British bomber in Rotterdam, that operated on a wavelength of 9.7 cm. With the radar, it was assumed that British aeroplanes could detect the U-boat while surfaced, without alerting the U-boat and could attack them by surprise. Indeed, the Royal Air Force had begun to do that within the Bay of Biscay, but not anywhere else. Dönitz accepted Maertens view that the Enigma Key M infrastructure was secure. Dönitz wrote in his war diary:


 * With the exception of two of three doubtful cases, enemy information about the position of our U-boats appears so have been maintained mainly from extensive use of airborne radar, and the resultant plotting of these positions has enabled him [the enemy] to organize effective diversion of convoy traffic.

In early May 1943, Donitz fired Maertens, for reasons that went beyond his fears about crypto-security and sent him to run the Kriegsmarine shipyard in Kiel.

Stichwort procedure
One reason for Maertens and the Kriegsmarine very high confidence in the Enigma Cipher machine was the incorporation of a very secret procedure that they believed would thwart any possibility of cracking the code. This was the Stichwort permutation (Stichwort), a procedure that the Kriegsmarine had introduced that completely altered the Naval Enigma cipher machine inner and outer key settings that were given on the printed settings list.