As a direct result of the capture of the British steamer City of Baghdad's secret code books by the German surface raider Atlantis in July 1940, the Nazis were able to de-cypher Admiralty convoy plans with deadly effect. Admiral Doenitz, aware of the movements of the Allied convoys, marshalled as many of his U-boats as possible.This book describes the resulting appalling Allied losses suffered by four convoys during the Autumn of 1940. The first convoy, SC2, consisting of fifty-three merchantmen, was attacked in early September by four U-boats. Due to poor weather only five ships were lost. Shortly afterwards, HX72, sailing from Nova Scotia, lost eleven of its forty-one ships to five Type VIIC U-boats. Top Aces Otto Kretschremer and Joachim Schepke, who penetrated inside the columns, accounted for nine.No less than nine U-boats attacked SC7 in October 1940. Of thirty-five merchantmen a staggering twenty were lost. Despite being a 'fast' convoy with ten escorts, HX79 also fared terribly losing twelve ships. In total forty-eight merchantmen were sunk and seven more damaged without any U-boat losses at all.A superbly researched and authoritative account of the darkest hours of the Battle of the Atlantic, The Wolf Packs Gather is a tragic account of unprecedented losses of seamen, ships and cargo from these merciless attacks on the four convoys. The Author, a much published and distinguished historian and Merchant Navy captain, is well qualified to describe not only the German tactics but the inadequacies of the Allied counter-measures.