The Battle of the Atlantic is one of the largest theatres of World War II, which defined how the war was to be conducted with incessant battles at sea. From September 1939, Germany had to seek every opportunity against Britain’s reliance on food imports and raw materials. At the same time, the U.S.S.R. needed imported equipment and supplies as a matter of urgency after the Wehrmacht’s attack in June 1941. In this regard, the task confronting the Allies was consequently to forge control of the seas to supply several second fronts, first in North Africa, then in Italy, and finally in Western Europe. Only the Anglo-American navies, together with the Canadian navy, could offset the unprecedented losses caused by German U-boats and Luftwaffe bombers. It was not until 1943 that the outcome of the struggle became certain.
From the American point of view, the battle went through three distinct phases. First, while maintaining neutrality, the U.S. continued to strengthen its naval preparedness. The “Two-Ocean Navy” legislation, signed into law that summer of 1940, was one such step; the next was what President Franklin Roosevelt did to aid Britain. That August, Roosevelt contrived a loan of older destroyers in return for access to British bases in the Western Hemisphere. In March 1941, the Lend-Lease Act voted credits to a hard-pressed Britain for supplies and equipment. By mid-1941, U.S. forces had seized bases in Greenland and Iceland.
In this early period, Germany had tried to avoid any direct challenge to American naval force. But the months before Pearl Harbor saw a rise in tensions. On September 4, 1941, a German submarine, under attack by a British plane, fired torpedoes at the USS Greer (DD 145) south of Iceland. Although neither side scored a hit, the incident led President Roosevelt to authorize Navy crews to fire on German U-boats on sight. On 31 October 1941, the USS Reuben James DD 245 was sunk by U-552 while escorting a convoy.
Despite improved readiness, the Navy was little better prepared to meet the German onslaught off the U.S. East Coast in the second phase of the Battle of the Atlantic. The first evidence of U-boats off the U.S. East Coast came on January 12, 1942, when the steamer Cyclops was torpedoed. German submarines in Operation Drumbeat relentlessly hunted tankers and merchantmen. The Navy had few destroyers and subchasers available, while aircraft were insufficient to patrol the coast. More than 80 merchantmen went down from January to April off the East Coast and 55 north of Bermuda to German submarines. By May, convoy systems, along with increased naval and air patrols, had forced U-boats to concentrate on the Gulf of Mexico and the Caribbean.
That fall, American escort forces convoyed 100,000 troops and their equipment to North Africa as part of Operation Torch without a loss. But once again the Germans adjusted their strategy, attacking in less well-guarded areas until the third phase got underway in May 1943. At this point, British and Canadian forces had reinforced defenses for North Atlantic convoys, while Admiral Ernest J. King had taken command of the Tenth Fleet, which coordinated American antisubmarine operations. It made all the difference, with the innovative scientific methods, long-range aircraft fitted with radar, and a large increase in escort carriers and destroyers to attack and defend. Added to this was British intelligence gained from intercepting German communications, helping immensely in pinpointing the U-boats. The massive U.S. industrial output of naval vessels and merchantmen began to pay off as well.
By mid-1943, the tide turned. Although German U-boat crews were incredibly courageous, the disadvantage under which they labored allowed Allied planners to execute land campaigns in Europe more confidently. The victory of the Allies in the Battle of the Atlantic was a testament to their ingenuity and fighting spirit, though not without learning some key lessons from World War I all over again. This struggle put an exclamation point on the need for escorted convoys, the proper mix of defense and offense, and the combining of technology with training.