Berlin, Germany November 29, 1939

On this date in 1939, nearly three months after the Wehr­macht (German armed forces) over­ran neigh­boring Poland, launching World War II in Europe, German dicta­tor Adolf Hitler issued Fuehrer Direc­tive Num­ber 9, the first of two direc­tives on mea­sures his coun­try would have to take to ren­der the British econ­omy and infra­struc­ture incap­able of sus­taining the war against Nazi Germany. “In the war against the Western Powers, . . . the con­quest of Britain is . . . the pre­req­ui­site for final victory,” Hitler wrote. “The most effec­tive means to achieve this is to para­lyze Britain’s eco­nomy through inter­rupting it at criti­cal points.” Titled “Prin­ciples for the Con­duct of the War against the Enemy’s Eco­nomy,” the focus of Direc­tive Num­ber 9 was, inter alia, on attacking British mer­chant and escort vessels, destroying port instal­la­tions, and inter­dicting the sea lanes between Britain’s over­seas empire and North America using air­craft, aerial-dropped magnetic mines (Luftminen in German), U‑boats, and S‑boats, or E‑boats as these fast torpedo boats were known to the Allies.

The British and later their North Ameri­can allies responded with naval and aerial convoy systems to protect the water life­line to the British Isles in this Battle of the Atlantic. The second of Hitler’s direc­tives, Num­ber 23, “Conduct of the War Against the English War Eco­nomy,” issued on Febru­ary 6, 1941, acknow­ledged that the mea­sures taken during the pre­ceding four­teen months had not so far had any “dis­cern­ible” effect on British morale or their capacity to “resist.” Direc­tive Num­ber 23 doubled-down on destroying British shipping using the Kriegs­marine’s growing fleet of new Type VII U‑boats under the com­mand of Rear Admiral Karl Doenitz. “The sinking of merchant­men is more impor­tant than [an] attack on enemy war­ships,” in Hitler’s esti­ma­tion. “By reducing the avail­able enemy ton­nage, not only will the block­ade, which is deci­sive to the war, be inten­si­fied, but enemy operations in Europe or Africa will be impeded.”

With the prospect of moving substan­tial Luft­waffe units from the French Channel coast to the East­ern Front for Opera­tion Bar­ba­rossa (June 1941), Germany’s planned liqui­da­tion of the Soviet Union in eight to ten weeks, Hitler thought it was pos­sible to keep the British off balance by pro­gres­sively stepping up sub­ma­rine opera­tions against mer­chant shipping in coor­di­nation with bombing the key centers of mili­tary air­craft pro­duction to both inflict the greatest pos­sible damage and simu­late the appear­ance of a German inva­sion of their isles, code­named Opera­tion Sea Lion, or Unter­nehmen See­loewe in German. (The one small-scale Sea Lion test exer­cise off Bou­logne, south­west of Calais in German-occu­pied North­ern France, con­ducted in good wea­ther and good visi­bility, with no navi­ga­tion hazards or enemy defenses to con­tend with, por­tended a dicey, even unsuc­cess­ful am­phib­ious assault on South­ern England. “An undeni­able fiasco,” was how one German admiral char­ac­terized the dress rehearsal.) Thus, the period from 1940 to 1942 repre­sented the best chance Germany had to win the Battle of the Atlantic: indeed, during this time frame 973 Allied ships were lost. And up through 1943 the Kriegs­marine, with as many as 100 U‑boats at sea at any time (Janu­ary 1943), came terrifyingly close to winning the Battle of the Atlantic.

German U-Boats and the Earliest Days of the Battle of the Atlantic

Battle of the Atlantic: Hvalfjord Allied naval base, Iceland, late June 1942Battle of the Atlantic: British escort destroyer on antisubmarine duty, October 1941

Left: Escorts and merchant ships at the Hvalfjord (Hval­fjörður) naval base, Iceland, late June 1942. During the World War II nearly one-third of the world’s mer­chant shipping was British. Out of 36,000 mer­chant sea­men who lost their lives between 1939 and 1945, over 30,000 were from the British Mer­chant Navy. More than 2,400 British ships were sunk out of the total of 2,900 Allied ships lost, or a loss of 14.6 million gross tons. A little over 9,500 U.S. mer­chant marines died at sea, in POW camps, or of their wounds out of the roughly 243,000 who served. (The U.S. govern­ment never kept accu­rate records for its mer­chant marine.) Most of the ships sunk during the Battle of the Atlantic were not in convoys, but sailing alone, or had become separated from convoys.

Right: Officers on the bridge of an escorting British destroyer keep a sharp lookout for enemy submarines, October 1941.

Battle of the Atlantic: U-boat shells merchant shipBattle of the Atlantic: Torpedoed U.S. tanker "Dixie Arrow", March 26, 1942

Left: An unnamed U-boat shells a merchant ship that had remained afloat after being torpe­doed (no date). The focus on U‑boat suc­cesses—the “aces” and their scores, the num­ber of con­voys attacked, and the ships sunk—ob­scures the fact that during the Battle of the Atlantic only 10 per­cent of trans­atlantic con­voys were ever attacked, and of those attacked only 10 per­cent on aver­age of the ships were lost. Over­all, more than 99 per­cent of all ships sailing to and from Great Britain during World War II did so safely.

Right: The 8,046-ton U.S. tanker Dixie Arrow was torpe­doed by U‑71 on March 26, 1942, off North Caro­lina’s Cape Hat­ter­as. The unescorted, unarmed ship is shown crumbling amid­ships under the heat of fire. Twenty-two crew­members out of 33 on board were rescued by a U.S. destroyer. Between June 1, 1941, and May 31, 1943, U‑71 carried out ten war patrols. Operating out of the huge U‑boat pens at St. Nazaire in occupied France, U‑71 on her fifth foray sank 38,894 tons of shipping between March and April 1942. She was scuttled on May 2, 1945, in Wilhelms­haven, Germany, several days before the country’s surrender.

Battle of the Atlantic: "U-288" under attack, April 3, 1944Battle of the Atlantic: Operation Torch convoy, November 1942

Left: A Grumman TBF Avenger of the Royal Navy’s Fleet Air Arm fires its machine gun at the conning tower of U‑288 during a con­voy run to the Soviet Union, April 3, 1944. The U‑boat was eventually sunk by rockets and depth charges. Forty-nine men died; there were no sur­vivors. The Kriegs­marine lost a total of 783 sub­ma­rines and 30,000 sail­ors during the war. Despite their best efforts, German sub­ma­rines failed to stop the flow of stra­te­gic supplies to Britain. Between existing Allied mer­chant ships, U.S.-built Liberty ships (totaling 38.5 million tons), and hundreds of British-built Empire ships, the Allies launched millions more ship tonnage than the 14 million tons of shipping lost to the U‑boat menace.

Right: At the height of the Atlantic campaign U‑boats failed to hin­der or even detect the U.S. invasion fleet headed to North Africa in November 1942 (Opera­tion Torch), and they failed to pre­vent the buildup of troops and supplies needed for the D-Day landings in June 1944. As early as May 1943, when a fifth of his U‑boats was sunk in “Black May,” Adm. Doenitz conceded that Germany had lost the Battle of the Atlantic.

Snipers of the Ocean: U-Boats of the Kriegsmarine and the Earliest Days of the Battle of the Atlantic