from within the columns of merchantmen in the convoy. The escort vessels, which were too few in number and often lacking in endurance, had no answer to the lone submarine attacking on the surface at night as their ASDIC detection apparatus only worked against underwater targets. Pack tactics were first used successfully in October 1940, to devastating effect in the battles of Convoys SC 7 and HX 79. Convoy SC 7, with a weak escort of two sloops and two corvettes, was overwhelmed, losing 59% of its ships. The battle for Convoy HX 79 was in many ways worse than SC 7. The loss of a quarter of the convoy without any loss to the U-boats despite a strong escort of two destroyers, four corvettes, three naval trawlers and a minesweeper demonstrated the utter inadequacy of the contemporary British anti-submarine tactics. The success of pack tactics against these two convoys encouraged Admiral Dönitz to adopt the wolf pack as his standard tactics. The change in British tactics included the introduction of permanent escort groups to improve the co-ordination and effectiveness of ships and men in battle. Initially, the escort groups consisted of two or three destroyers and half a dozen corvettes. Since two or three of the group would usually be in dock repairing weather or battle damage, the groups typically sailed with about six ships. The Germans also made use of long-range patrol aircraft to find convoys for the U-boat packs to attack, though this tactic rarely succeeded. Towards the end of the war the Germans introduced homing-torpedoes that aimed for the noise made by a target's propellers. Although devastatingly effective at first, the Allied scientists soon developed countermeasures. The American submarine campaign in the Pacific contains many parallels with the German submarine campaign in the Atlantic. Like the Germans, the Americans began the war with a flawed weapon – faulty torpedoes – that undermined morale and took more than a year to fix. American submariners developed the same preference for attacking on the surface at night and similar pack tactics, although American wolf packs rarely exceeded three boats. But in the Pacific, it was the submarines, not the escorts, that benefited from the introduction of new technologies like radar. By 1943 many US submarines were fitted with radar, which American submarines were routinely using to find convoys and track the positions of escorts at night. Development of anti-submarine