 As western Atlantic coastal convoys brought an end to the "second happy time", Admiral Karl Dönitz, the "Befehlshaber der U-Boote" ("BdU") or commander in chief of U-boats, shifted focus to the mid-Atlantic to avoid aircraft patrols.Although convoy routing was less predictable in the mid-ocean, Dönitz anticipated that the increased numbers of U-boats being produced would be able to effectively search for convoys with the advantage of intelligence gained through "B-Dienst" decryption of British Naval Cypher Number 3.However, only 20 percent of the 180 trans-Atlantic convoys sailing from the end of July 1942 until the end of April 1943 lost ships to U-boat attack.