Editing Karl Dönitz (section)

===Intelligence battle===
Intelligence played an important role in the Battle of the Atlantic.{{sfn|Gardner|1999|pp=1–218}} In general, BdU intelligence was poor.{{sfn|Syrett|1994|p=117}}{{sfn|Gardner|1999|p=58}} 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.{{sfn|Boog|Rahn|Stumpf|Wegner|2001|p=343}} Radio traffic compromised his ciphers by giving the Allies more messages to work with. Furthermore, replies from the boats enabled the Allies to use [[High-frequency direction finding]] (HF/DF, called "Huff-Duff") to locate a U-boat using its radio, track it and attack it.{{sfn|Stern|2003|p=171}}{{sfn|Syrett|1994|p=264}} 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 ample intelligence.{{sfn|Syrett|1994|p=264}} 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.{{sfn|Syrett|1994|p=264}} 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.{{sfn|Syrett|1994|p=264}} In contrast to the Allies, the {{lang|de|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.{{sfn|Syrett|1994|pp=264–265}} These Allied advantages failed to avert heavy losses in the June 1940{{snd}} May 1941 period, known to U-boat crews as the "[[First Happy Time]]."{{sfn|Stern|2003|p=112}} In June 1941, 68 ships were sunk in the North Atlantic ({{GRT|318,740|link=off}}) 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.{{sfn|Terraine|1989|p=767}}

On 7 May 1941, the Royal Navy captured the German Arctic meteorological vessel {{lang|de|München}} and took its [[Enigma machine]] intact, which allowed the Royal Navy to decode U-boat radio communications in June 1941.{{sfn|Tucker|2005|p=143}} Two days later the capture of [[German submarine U-110 (1940)|''U-110'']] was an intelligence coup for the British. The settings for high-level "officer-only" signals, "short-signals" ({{lang|de|Kurzsignale}}) and codes standardising messages to defeat HF/DF fixes by sheer speed were found.{{sfn|Terraine|1989|p=326}} Only the ''Hydra'' settings for May were missing. The papers were the only stores destroyed by the crew.{{sfn|Terraine|1989|p=326}} The capture on 28 June of another weather ship, {{lang|de|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.{{sfn|Tucker|2005|p=143}} The capture of the ''U-110'' allowed the [[British Admiralty|Admiralty]] to identify individual boats, their commanders, operational readiness, damage reports, location, type, speed, endurance from working up in the [[Baltic Sea|Baltic]] to Atlantic patrols.{{sfn|Terraine|1989|p=326}} On 1 February 1942, the Germans had introduced the [[Kriegsmarine M4|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 lanes 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 lanes were secured, which came as a great surprise to Dönitz.{{sfn|Tucker|2005|p=145}} The lack of intelligence and increased numbers of U-boats contributed enormously to Allied losses that year.{{sfn|Hinsley|1993|p=157}}

[[File:Angelo Parona and Karl Doenitz.jpg|thumb|upright|Dönitz and his Italian counterpart Admiral [[Angelo Parona]] in 1941]]
Signals security aroused Dönitz's suspicions during the war. On 12 January 1942 [[German submarine U-459|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.{{sfn|Macksey|2000|p=23}} 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 investigations, the conclusion of the BdU staff was that ''Enigma'' was impenetrable. His signals officer responded to the ''U-459'' incident with answers ranging from coincidence, direction finding, to Italian treachery.{{sfn|Macksey|2000|p=23}} General [[Erich Fellgiebel]], Chief Signal Officer of Army High Command and of Supreme Command of Armed Forces ({{lang|de|Chef des Heeresnachrichtenwesens}}), apparently concurred with Dönitz. He concluded that there was "convincing evidence" that, after an "exhaustive investigation" that the Allied codebreakers had been reading high level communications.{{sfn|Macksey|2000|p=53}} Other departments in the navy downplayed or dismissed these concerns. They vaguely implied "some components" of Enigma had been compromised, but there was "no real basis for acute anxiety as regards any compromise of operational security".{{sfn|Kohnen|1999|p=65}}