The wolf pack
was a tactic employed by the German kriegsmarine U-boat
forces during World War II
. It was introduced by Grossadmiral Karl Dönitz
, commander of the U-boat forces, as a counter to the Allied
use of the convoy
system during the Battle of the Atlantic
The convoy protected shipping by collecting large numbers of merchant vessels in a group, under the guns of available escorts. The convoy would steam across the Atlantic at the maximum maintainable speed of the slowest ship, and randomly 'zig-zag' across its base course. When U-boats were spotted, the escorts (typically destroyers, which were faster than the merchies) would rush them in an attempt to either destroy them with depth-charges or gunfire, or at the least force them to submerge. The reasoning was simple - if you could force the U-boat to submerge for long enough, it would fall behind the fast-moving convoy, since submerged speeds for submarines were typically measures under a dozen knots - and at that speed, their endurance dropped to one or two hours before exhausting their batteries. While the U-boat was attempting to evade the convoy escorts, the merchant ships would rush past it - and although the U-boat could make slightly better speed than merchant vessels on the surface, that would render it very vulnerable.
The wolf pack was Dönitz's answer to the convoy. U-boats were spread across the convoy routes in patrols. As soon as a U-boat spotted a convoy, it would give chase, radioing the convoy's position, course and speed to headquarters in Europe (Befelshaber der Unterseeboote, or BdU - also Dönitz's title) using the Enigma encryption system. BdU would direct other U-boats on station in the path of the convoy to intercept it - timed so that they would converge for the attack at night, so that they could run on the surface for best speed and torpedo accuracy. This sudden convergence of U-boats was the wolf pack (or as the Kriegsmarine called it, Rudeltaktik). Once the attack was made, U-boats attacking from multiple angles could 'split' the escorts, and if there were enough of them, one or more would get an unopposed torpedo run. Furthermore, the escorts would not be able to keep *all* of them below the surface for long; if they tried to split their attentions, the 'abandoned' U-boats would pop back up, make a surface 'sprint' run to get ahead of the convoy again if possible, and attack once more.
Air cover made the wolf pack ineffective, since aircraft would attack any submarine found on the surface. With airborne radar, submarines were no longer safe during the day or night when lying up to recharge their batteries. Radar had improved by the end of the war to the point that the snorkels of submarines at periscope depth running diesel engines could be detected by radar sets onboard naval patrol aircraft and attacked. Even if not destroyed, these boats would be unable to acquire a battery charge and would be unable to make speed surface runs to intercept convoys and thus were effectively neutralized.
The Allies countered the wolf pack with air cover and intelligence; intercepts from theKriegsmarine radio communications channels were used (once the Naval Enigma had been cracked) to pinpoint the locations of the resupply submarines used to allow the U-Boats to operate at extreme ranges from their European bases. These boats, known as milch cows (milk cows) would be targeted by scheduling information intercepted over the radio. When their supply submarine was destroyed, a wolf pack would be forced to either return to base or dramatically curtail operations until the boats could be resupplied.