Atlantic, Battle of the (1939–1945) also broke the Allied escort code, Naval Code #3 That gave the U-boats an advantage that lasted until new codes were introduced in May 1943 But it was principally lack of coastal convoys and sufficient escorts to form them that permitted the extraordinary slaughter: 65 out of 71 ships sunk in February had steamed as independents The USN formed coastal Bucket Brigades in April as an interim measure that proved partially successful Dönitz therefore shifted many of his U-boats from Florida into the Caribbean, where Gulf Coast oil tankers abounded and many still sailed unescorted The main North Atlantic convoys were less molested during this period, as most U-boats were happily sinking ships farther south The situation improved over the second half of 1942 The RN, RCN, and USN coordinated and systematized convoy planning, added more escort ships, deployed the first true escort carriers, and stretched land-based air cover from every available base using new and longer-range aircraft Older twin-engine bombers were handed over to Coastal Command and the USN, as four-engine heavy bomber types replaced them in the air war over Germany A few four-engine aircraft were provided, and more fighters were redeployed from southern England to intercept Kondors and other German aircraft operating out of the Bay of Biscay Not all went smoothly, and the naval war remained in doubt to those fighting it After ONS154 lost 14 of its 46 ships in December 1942, the Royal Navy sharply rebuked the responsible RCN escort group and temporarily withdrew all Canadian escort groups from the battle, ordering crews to undergo intensive ASW retraining They were replaced by RN groups returning from North Africa after escorting troop and supply ships of the TORCH landings It was a real humiliation for the Canadians, but mostly reflected the fact that too many RCN crews were necessarily rushed into escort duty only half-trained during the dark days when even a poorly trained crew was desperately needed Once retrained and back in battle the same RCN crews and their successors achieved an admirable record The Germans were having troubles of their own If measured by BdU’s key metric of tonnage sunk per U-boat per day (“Tonnagekrieg”), the tide of war in the Atlantic appears to have turned by the end of 1941 That was even before full commitment by the USN to the fight Some historians have even argued that the battle at sea against the U-boats was already won by that date and that only secret British calculation to frighten and manipulate the Americans into committing major naval forces to the Atlantic explains the nearly universal wartime view that the fight was far from over at the start of 1942 Statistics are tricky things, but they support marking a much later date as the point the fortunes of battle actually turned in the Atlantic U-boats sank nearly 1,300 ships in 1941, and another 1,662 during 1942 That meant the Allies lost million GRT in 1942 alone, a figure greatly increased by losses of unescorted independents in American seas in the first half of the year Even though Allied shipyards were producing more ships at faster rates, and escorts and aircraft were sinking more U-boats, German production of U-boats meant more attack craft were also available to Dönitz In German and British propaganda, public perception at the time, and in secret intelligence appraisals, the final shift of fortunes in the Atlantic did not truly favor the Allies until mid-1943 U.S shipyards were by then building far more Liberty 91