Between September 1939 and December 1941, the United States moved from neutral to active belligerent in an undeclared naval war against Nazi Germany. During those early years the British could well have lost the Battle of the Atlantic. The undeclared war was the difference that kept Britain in the war and gave the United States time to prepare for total war.With America’s isolationism, disillusionment from its World War I experience, pacifism, and tradition of avoiding European problems, President Franklin D. Roosevelt moved cautiously to aid Britain. Historian C.L. Sulzberger wrote that the undeclared war “came about in degrees.” For Roosevelt, it was more than a policy. It was a conviction to halt an evil and a threat to civilization. As commander in chief of the U.S. armed forces, Roosevelt ordered the U.S. Navy from neutrality to undeclared war.
It was a slow process as Roosevelt walked a tightrope between public opinion, the Constitution, and a declaration of war. By the fall of 1941, the U.S. Navy and the British Royal Navy were operating together as wartime naval partners. So close were their operations that as early as autumn 1939, the British Ambassador to the United States, Lord Lothian, termed it a “present unwritten and unnamed naval alliance.” The United States Navy called it an “informal arrangement.”
Regardless of what America’s actions were called, the fact is the power of the United States influenced the course of the Atlantic war in 1941. The undeclared war was most intense between September and December 1941, but its origins reached back more than two years and sprang from the mind of one man and one man only—Franklin Roosevelt.
Two Navies Unprepared For War
When war broke out in September 1939, the Royal Navy and the German Kriegsmarine were both unprepared. Land-minded Adolf Hitler prepared his army and air force but had not given his navy time to build the necessary submarine or surface fleets for a naval war against Britain. Since Hitler planned for a war of short duration, he considered interference with the Atlantic sealanes a means to defeat Britain. However, Hitler preferred to eliminate continental powers first and then make the British “see reason.”
The German naval staff, led by Grand Admiral Erich Raeder, and the U-Boat Service, commanded by Admiral Karl Dönitz, held the opposite view of the war. They were convinced it would be a long war and that it would have to be won in the Atlantic. The Kriegsmarine believed that Britain had to be hit decisively in the Atlantic theater before America’s power and economic impact became decisive. Dönitz believed that 300 submarines and wolfpack tactics could strangle Britain. But Hitler launched the war almost three years before the naval construction program was completed. This left the German Navy short of submarines and surface vessels. At the start of the war, Hitler also restricted the U-boat campaign.
The British instituted the convoy system at the start of the war. First Lord of the Admiralty Winston Churchill remembered the lessons of World War I and reestablished the convoys. However, the Royal Navy engaged in the war sooner than they hoped. The British shipbuilding program, especially escorts, would not produce results until 1941. Until the new escorts came on line, a convoy escort limit had to be drawn about 300 miles west of the British Isles.
The British convoys had four major weaknesses: (1) a shortage of escorts, usually two or three ships; (2) ASDIC (a method of underwater detection) was ineffective beyond 1,000 yards; (3) RADAR (improved detection) was too primitive to give early or accurate warnings of night attacks; and (4) lack of air cover. As much as the Royal Navy lacked at the start of the war, it did have the capacity to blockade Germany, bottle up most of the German surface fleet, and handle the few U-boats and raiders that operated on the high seas.
But Churchill, unlike Hitler, recognized that the war would be a long, total war. As such, he saw the escort shortage as a major weakness. Churchill thought Roosevelt might be persuaded to sell Britain fleet destroyers to fill the urgent need for open-ocean escorts for convoys and inquired about such an arrangement in September 1939. The situation at the outset was decidedly in favor of the Allies.
America’s Inevitable War
The Munich Pact and the failure of appeasement convinced Roosevelt that Germany remained a dangerous threat and that war was inevitable. Roosevelt’s policy for America was dictated by a desire to stay out of war, support the Allies, and prepare America’s defenses. Gerhard Weinberg, in A World at War, wrote, “The American President hoped to avoid open warfare with Germany altogether. He urged his people to aid Britain and he devised a whole variety of ways to do just that; but he hoped until literally the last minute the United States could stay out of war.”