The Wolfpack (Rudeltaktik) was a convoy attack tactic employed in the Second World War. It was used principally by the U-boats of the Kriegsmarine during the Battle of the Atlantic, and by the submarines of the United States Navy in the Pacific War. The idea of a co-ordinated submarine attack on convoys had been proposed during the First World War but had had no success. In the Atlantic during the Second World War, the Germans had considerable successes with their wolfpack attacks but were ultimately defeated by the Allies of World War II. In the Pacific, the American submarine force was able to devastate the Japanese merchant marine, though this was not solely due to the wolfpack tactic. Wolfpacks fell out of use during the Cold War as the role of the submarine changed.
World War I During the Handelskrieg (German war on trade) Allied ships travelled independently prior to the introduction of the convoy system and were vulnerable to attacks by U-boats operating as 'lone wolves'. By gathering up merchant ships into convoys the British Admiralty denied them targets and presented a more defensible front if found and attacked. The logical remedy for the U-boat Arm was to gather U-boats similarly into attacking formations. In early 1917 Hermann Bauer, the Commander of the High Seas U-boats (Führer der Unterseeboote [FdU]) proposed establishing patrol lines of U-boats across convoy routes, in order to mass for attack on any convoy reported. These boats would be supported by a forward base on land and a headquarters and supply vessel, such as the Deutschland-class converted U-cruisers equipped with radio and supplies of fuel and torpedoes. The shore station would monitor radio transmissions and the commander in the HQ boat would co-ordinate the attack. This proved easier to propose than to carry out and proved disastrous when tried. In May 1918 six U-boats under the command of KL Rucker, in U-103, were operating in the English Channel; U-103 made contact with a troop convoy but was rammed and sunk by the troopship Olympic before she could attack. U-70 found convoy HS 38 but managed only one torpedo attack, which missed. UB 72 was caught on the surface by British submarine D4, torpedoed and sunk. During the period of operation, 19 homeward and 11 outward convoys passed through the patrol area without loss and two U-boats (a third of the force) had been destroyed. In October 1918 another attempt at a co-ordinated attack was made in the Mediterranean, when two U-boats attempted a co-ordinated attack on a convoy. One of them was sunk and its commander, ObLt Karl Dönitz, was taken prisoner.
Inter war years During the interwar years the German Navy was forbidden to have U-boats but began to re-arm in 1935. Under Karl Dönitz as FdU developed co-ordinated attack tactics based on Bauer's plan and his own experience and trials of the new tactics in 1936 proved successful. Dönitz called his strategy of submarine warfare Rudeltaktik, which literally translates as "pack tactic" but referred specifically to the hunting tactics of wolves and submarines were known by their nickname of graue Wölfe (grey wolves).
U-boats in the Second World War
With the outbreak of the Second World War the U-boat Arm found the success of the pre-war trials had created some complacency; when these tactics were first tried in October 1939 (Hartmann's wolfpack) they were a failure; Hartmann found he was unable to exercise any tactical control from his boat at sea and the convoy attack was unsuccessful, while three U-boats were lost in the operation. A second attempt the following month also failed. A further attempt in June 1940 following the Norwegian campaign (Rösing's wolfpack) also failed, leading to a re-think of German tactics.
Rudeltaktik The revised approach saw Dönitz micromanaging operations at sea from his headquarters in occupied France, relying on the supposedly unbreakable Enigma code to transmit and receive orders and co-ordinate movements. U-boat movements were controlled by U-boat Command (BdU) from Kerneval. U-boats usually patrolled separately, often strung out in lines across likely convoy routes to engage merchant ships and small vulnerable destroyers, being ordered to congregate only after one located a convoy and alerted the BdU. Rudeltaktik (pack tactics) consisted of as many U-boats as could reach the scene of the attack. With the exception of the orders given by the BdU, U-boat commanders could attack as they saw fit. Often they were given a probable number of U-boats that would arrive and when they were in contact with the convoy, make call signs to see how many had arrived. If their number were sufficiently high compared to the expected threat of the escorts, they would attack. This led to a series of successful pack attacks on Allied convoys in the latter half of 1940 (known as "the Happy Time" to the U-boat men).
Drawbacks While the German pack tactic was effective, it had several drawbacks. Most notably, wolfpacks required extensive radio communication to coordinate the attacks. This left the U-boats vulnerable to a device called the High Frequency Direction Finder (HF/DF or Huff-Duff), which allowed Allied naval forces to determine the location of the enemy boats transmitting and attack them. The pack tactic was able to bring about a force concentration against a convoy but no tactics for co-ordinated attack were developed; each commander present was left to move against the convoy as he saw fit. The escort groups developed group tactics against U-boat attack, gaining an advantage. As packs got larger the risks from this lack of co-ordination increased, such as overlapping attacks, collision or friendly fire incidents (in May 1943 for example, two U-boats stalking a Gibraltar convoy, U-439 and U-659 collided, with the loss of both). Away from the Atlantic, the U-boat Arm had less scope for pack attacks; Operation Drumbeat against US shipping in early 1942, off the US eastern coast, and Operation Neuland in the Caribbean, were conducted by U-boats on individual patrol, until the introduction of a convoy system there saw the U-boats withdraw to easier hunting grounds. In the South Atlantic and the Indian Ocean individual routing by the Allies and small numbers of U-boats active there again saw the employment of the lone wolf approach by the U-boat Arm.
Countermeasures
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