page_title: Karl Dönitz
section_title: Intelligence war
hierarchical_section_title: Karl Dönitz / World War II / Intelligence war
caption_attribution_description: English: Italian Admiral Angelo Parona (1889-1977) with Karl Donitz.
context_page_description: Karl Dönitz was a German admiral during the Nazi era who briefly succeeded Adolf Hitler as the German head of state in 1945. As Supreme Commander of the Navy since 1943, he played a major role in the naval history of World War II. The Nuremberg Trials court convicted him of war crimes in 1946.
  He began his career in the Imperial German Navy before World War I. In 1918, he was commanding UB-68 when she was sunk by British forces. Dönitz was taken prisoner. While in a prisoner of war camp, he formulated what he later called Rudeltaktik.
  At the start of World War II, he was the senior submarine officer in the Kriegsmarine, known as Befehlshaber der Unterseeboote. In January 1943, Dönitz achieved the rank of Großadmiral and replaced Grand Admiral Erich Raeder as Commander-in-Chief of the Navy. Dönitz was the main enemy of Allied naval forces in the Battle of the Atlantic. From 1939–1943 the U-boats fought effectively but lost the initiative from May 1943. Dönitz ordered his submarines into battle until 1945 to relieve the pressure on other branches of the Wehrmacht. 648 U-boats were lost—429 with no survivors. Furthermore, of these, 215 were lost on their first patrol.
context_section_description: Intelligence played an important role in the Battle of the Atlantic. In general, BdU intelligence was poor. Counter-intelligence was not much better. At the height of the battle in mid-1943 some 2,000 signals were sent from the 110 U-Boats at sea. Radio traffic compromised his ciphers by giving the Allies more messages to work with. Furthermore, replies from the boats enabled the Allies to use direction finding (HF/DF, called "Huff-Duff") to locate a U-boat using its radio, track it and attack it. The over-centralised command structure of BdU and its insistence on micro-managing every aspect of U-boat operations with endless signals provided the Allied navies with enormous intelligence. The enormous "paper chase" [cross-referencing of materials] operations pursued by Allied intelligence agencies was not thought possible by BdU. The Germans did not suspect the Allies had identified the codes broken by B-Dienst. Conversely, when Dönitz suspected the enemy had penetrated his own communications BdU's response was to suspect internal sabotage and reduce the number of the staff officers to the most reliable, exacerbating the problem of over-centralisation. In contrast to the Allies, the Wehrmacht was suspicious of civilian scientific advisors and generally distrusted outsiders. The Germans were never as open to new ideas or thinking of war in intelligence terms. According to one analyst BdU "lacked imagination and intellectual daring" in the naval war. These Allied advantages failed to avert heavy losses in the June 1940 –  May 1941 period, known to U-Boat crews as the "First Happy Time." In June 1941, 68 ships were sunk in the North Atlantic (318,740 GRT) at a cost of four U-Boats, but the German submarines would not eclipse that number for the remainder of the year. Just 10 transports were sunk in November and December 1941.
  On 7 May 1941, the Royal Navy captured the German Arctic meteorological vessel München and took its Enigma machine intact, this allowed the Royal Navy to decode U-boat radio communications in June 1941. Two days later the capture of U-110 was an intelligence coup for the British. The settings for high-level "officer-only" signals, "short-signals" (Kurzsignale) and codes standardising messages to defeat HF/DF fixes by sheer speed were found. Only the Hydra settings for May were missing. The papers were the only stores destroyed by the crew. The capture on 28 June of another weather ship, Lauenburg, enabled British decryption operations to read radio traffic in July 1941. Beginning in August 1941, Bletchley Park operatives could decrypt signals between Dönitz and his U-boats at sea without any restriction. The capture of the U-110 allowed the Admiralty to identify individual boats, their commanders, operational readiness, damage reports, location, type, speed, endurance from working up in the Baltic to Atlantic patrols. On 1 February 1942, the Germans had introduced the M4 cipher machine, which secured communications until it was cracked in December 1942. Even so, the U-boats achieved their best success against the convoys in March 1943, due to an increase in U-boat numbers, and the protection of the shipping lines was in jeopardy. Due to the cracked M4 and the use of radar, the Allies began to send air and surface reinforcements to convoys under threat. The shipping lines were secured, which came as a great surprise to Dönitz. The lack of intelligence and increased numbers of U-boats contributed enormously to Allied losses that year.
  Signals security aroused Dönitz's suspicions during the war. On 12 January 1942 German supply submarine U-459 arrived 800 nautical miles west of Freetown, well clear of convoy lanes. It was scheduled to rendezvous with an Italian submarine, until intercepted by a warship. The German captain's report coincided with reports of a decrease in sightings and a period of tension between Dönitz and Raeder. The number of U-boats in the Atlantic, by logic, should have increased, not lowered the number of sightings and the reasons for this made Dönitz uneasy. Despite several investigati
caption: Dönitz and his Italian counterpart Admiral Angelo Parona in 1941
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