“The only thing that ever really frightened me during the war was the U-boat peril. I was even more anxious about this battle than I had been about the glorious air fight called the Battle of Britain.” — Winston Churchill
Prior to embarking on a closer examination or analysis of any battle, it is important to first understand the problem. In the Battle of the Atlantic, the unequivocal problem was the danger posed by German U-boats to merchant convoys traversing the Atlantic Ocean. These convoys constituted the lifeline to the forces prosecuting the war on the European front. Without these critical supplies, the Allies would have been hard-pressed to remain in the war. Churchill labeled this U-boat peril as “the only thing that ever really frightened [him],” even more so than the “glorious air fight called the Battle of Britain.”
Capture, Surrender, and Rudeltaktik
Early in the battle, three key events took place that would tip the scales in favor of Germany – if only for a time: the capture of Normandy, the subsequent occupation of France, and the introduction of rudeltaktik, or “pack tactics”. The first two events provided Germany’s U-boats with ready access to the North Atlantic, further from British mining and air patrols, as well as bases along the Atlantic coast of France “which greatly increased the number of U-boats actually at sea.” The ability to put more U-boats at sea directly contributed to the eventual success of the third event: the use of rudeltaktiks – more commonly referred to as “wolf-pack tactics”.
Initially devised by Admiral Dönitz as early as 1935 — and later improved upon — rudeltaktiks were designed specifically to counter Britain’s use of convoys. These tactics consisted of a concave curve of U-boats stretched across known or suspected Allied convoy routes. As the convoys would pass through, the first U-boat to detect the convoy would act as a “shadower” and would relay initial and updated contact information back to headquarters where Admiral Dönitz closely controlled all U-boat operations. Upon receiving the contact report, Admiral Dönitz would then direct and vector the other submarines in the pack onto the target.
Another aspect of these tactics was, though they were conducted by submarines, they were done so on the surface. This was based on Admiral Dönitz’ belief that “the submarine was primarily a surface craft that had the useful ability to dive beneath the surface when necessary.” Accordingly, Dönitz implemented the “coordinated attack tactics, taking advantage of the submarine’s tiny silhouette, hard for escort vessels to spot at night, and of its speed on the surface, much greater than that of the ships making up the convoy.” The fundamental purpose of these wolf-pack tactics was to inflict maximum damage on the enemy – and, indeed, they did – particularly during two specific periods in the battle.
These two periods were referred to by the Germans as “Happy Times.” The first “Happy Time” took place between July 1940 and March 1941 in the waters off of Britain and the Atlantic Ocean. Though Germany’s effective use of pack tactics had not yet been perfected at the beginning of this phase, the July occupation of French Atlantic ports by the Axis significantly increased the number of targets vulnerable to attack. Between July and October 1940 alone, 282 Allied ships were sunk accounting for nearly 1.5 million tons. Although attacks on merchant shipping would remain high, this first “Happy time” ended in March 1941.
The second “Happy Time,” also known as the “American Shooting Season” or “Operation Drumbeat,” took place off the eastern coast of the United States from January 1942 until approximately August of that year. As its nickname suggests, this phase was one in which German U-boats enjoyed extreme successes against U.S. shipping and naval vessels following America’s entry into the war. Encountering weak and disorganized defenses, Germany’s offensive resulted in the sinking of more than 600 ships, 3 million tons, and the loss of thousands of lives.
The Allies’ responses to Germany’s successes were many and varied: the implementation of convoys, providing armed escorts for the convoys, increasing maritime air patrols, improving the use and effectiveness of radar and HFDF, and, finally, the ability to intercept and decrypt naval radio traffic. Dan Van Der Vat, in his book, Stealth at Sea, writes: “There was no single magic answer to the U-boat, nor would there be; but if there was one contribution which counted more than any other single factor…it was intelligence.” Breaking the German naval Enigma would be the single most important factor in gathering that very intelligence which would provide Allied forces the battlespace awareness necessary to solve the German U-boat problem.
 Miller, David. Great Battles of World War II: Major Operations that Affected the Course of the War. New York: Crescent Books, 1998.
 Parrish, Thomas. The Submarine: A History. New York: Penguin Books, 2005.