On December 11, 1941, Hitler declared war on the United States, and for Admiral Karl Dönitz, commander of Germany’s U-boat fleet, the moment was an opportunity. He saw America’s entry into the war as a chance to strike devastating blows in the tonnage war, the relentless campaign to sink Allied merchant shipping faster than it could be replaced. Dönitz immediately drafted plans for a campaign he called Operation Drum Beat, intending to send a dozen long-range Type IX U-boats from the Mediterranean to launch a surprise assault against the American East Coast. Hitler refused to weaken German and Italian forces in the Mediterranean, allowing only six boats.

By December 18, 1941, five long-range U-boats were ready for the long Atlantic crossing; a sixth had been withdrawn with mechanical trouble. The captains were ordered not to attack any ship under 10,000 tons until they reached their designated patrol zones, where they would remain on station for two weeks. Dönitz believed American coastal defenses were fragmented and disorganized, and he wanted maximum shock. The five commanders were to arrive at their positions and wait for his final order to strike simultaneously.

The patrol area stretched from the St. Lawrence River in Canada to Cape Hatteras on the North Carolina coast. By the evening of January 14, 1942, all five boats were on station, and Operation Drum Beat began. The commander of U-123, Kapitänleutnant Reinhard Hardegen, boldly maneuvered his boat into the outer limits of New York Bay.

What he saw shocked him. The coast was brightly lit. At Coney Island, a huge Ferris wheel and merry-go-rounds were visible. Ships sailed with navigation lights on, and lighthouses shone brightly.

Hardegen later recalled, simply, that they were not prepared at all. To him, it was incomprehensible. The sinkings came quickly. Dönitz’s “Gray Wolves” hunted unobserved along the American shore.

The initial five U-boats returned to base after destroying 23 ships, totaling over 150,000 tons. Hardegen’s own tally was eight ships, more than 50,000 tons, earning him the Knight’s Cross. Back at the U-boat base in Lorient, he confirmed Dönitz’s assessment that American waters were a good hunting ground and urged that the offensive be stepped up. Dönitz had already deployed additional boats, though he never had more than a dozen in action along the American coast at any one time.

Unknown to Dönitz, the U. S. Naval High Command was not surprised. British intelligence, decrypting Enigma signals, had warned that a large U-boat operation was about to begin off the North American seaboard.

On January 12, 1942, the Admiralty’s Submarine Tracking Unit in London had tracked a large number of U-boats heading for the U. S. East Coast. The warning, however, did little good.

As one account put it, it was equivalent to trying to save a condemned man by informing him of the length of rope with which the executioner was about to hang him. Admiral Ernest J. King, commander of the United States Fleet and chief of naval operations, bore responsibility for the eastern seaboard’s dismal readiness. His subordinate, Vice Admiral Adolphus Andrews, commander of the Eastern Sea Frontier, had warned him two months before the slaughter began that if enemy submarines operated off the coast, his command had no forces available to take adequate action.

King took no significant action. Andrews had only 20 mostly antiquated ships patrolling a coastline of 1,500 miles, including tugs, yachts, trawlers, schooners, and motor cruisers, manned primarily by enthusiastic amateur sailors. None could keep up with a U-boat running on the surface. The fleet was officially called the Coastal Picket Patrol Force, but its ineffectiveness earned it the nickname the “Donald Duck Navy.

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By January 1942, German U-boat crews had been at war for more than two years and were highly skilled at sinking ships. Unleashed on the relatively defenseless American coast, the consequences were lethal. By the end of February, 327,000 tons of shipping had gone down, most off the Eastern Seaboard. Dönitz was overjoyed and dispatched more boats to take positions off the coast and expand into the Caribbean.

To avoid detection, U-boats in a combat zone would often spend daylight hours on the ocean floor and hunt at night. But Hardegen and his fellow captains quickly realized this was unnecessary; the defenses simply did not exist. Towns and cities along the coast refused to impose blackouts for fear of losing tourist trade. From the cold Canadian coast to the tropical Caribbean, U-boats cruised freely, destroying unaccompanied freighters and tankers with impunity.

Their targets were essentially sitting ducks, silhouetted against the brightly lit shoreline. Most of the sunk merchant ships were unarmed, leaving their crews to endure the assault without any means of defense. On February 6, Winston Churchill, alarmed by the increasing losses in American waters, messaged President Roosevelt, asking him to pay special attention to the crisis. Ships were being sunk 30 miles or less offshore, making burning wrecks a common sight near coastal resorts.

While the one-sided battle raged on America’s doorstep, the public was fed a false narrative. Hardegen noted that German crews listened to American radio transmissions claiming U-boats had been sunk. “We were supposed to have been sunk three times,” he said. Every time they sank a ship, the Americans claimed another U-boat destroyed.

It was, he believed, a consolation the Americans needed. The slaughter continued in March, with the tonnage sunk equaling that of January and February combined. Two months into the offensive, the U. S.

Navy had not sunk a single Axis submarine. Mussolini dispatched Italian submarines to take advantage of what the Germans were calling the “American shooting season. ” Sir Dudley Pound, the British First Sea Lord, urged King to implement a convoy system, arguing that the Royal Navy had learned through bitter experience that patrols were ineffective. King, an anglophobe, rejected the advice, believing that independently sailing ships were less vulnerable than those bunched together in convoy without strong escort protection.

Britain’s experience, however, demonstrated that a poorly guarded convoy was preferable to no convoy at all. Dönitz’s campaign in the Caribbean was well underway, with a half dozen U-boats and several Italian submarines pillaging with alarming confidence. U-161 entered the harbor at Trinidad’s Port of Spain and torpedoed two tankers at anchor. U-156 slipped into Aruba’s port, torpedoed three tankers, shelled the oil terminal, and departed, demonstrating how unprepared the region’s defenses were.

On March 17, the situation became critical when U-124 torpedoed four tankers and a steamer off Cape Hatteras in a single night. It was clear the Donald Duck Navy could not handle the task. Andrews flew to Washington to plead with King for destroyers. King flatly refused.

Complaints poured in from Southern Florida to Atlantic City that the tourist season was being ruined by tankers burning in sight of sunbathers and oil slicks washing up on the beaches. Shocked by the scale of the losses, Churchill offered Roosevelt 24 armed trawlers and 10 corvettes manned by experienced sub hunters. Roosevelt gratefully accepted. By the end of May, 129 tankers had been lost in American waters, prompting the Petroleum Industry War Council to warn that unless the situation improved, America would run out of oil in six months.

Even so, there were signs of improvement. By the second week of May, two U-boats had been sunk, and coastal communities had finally been ordered to observe blackouts. The normally partisan official history was damning in its condemnation, calling the failure to dim waterfront lights one of the most reprehensible failures on the American part. Miami and its opulent suburbs cast a six-mile neon glow against which shipping was silhouetted.

Ships were wrecked and seamen drowned so that citizens could go about their business and enjoy themselves. As U-boats continued to destroy shipping in the Caribbean and along the American coast, Churchill and the Admiralty closely monitored their movements from London. Concerned about the lack of progress, Churchill pressed Roosevelt for drastic action. Roosevelt assured him everything was being done.

General George C. Marshall, the Army chief of staff, spoke with King, leaving him in no doubt about the gravity of the situation. The losses off the Atlantic Seaboard and in the Caribbean, he said, now threatened the entire war effort. Under pressure, King finally gave in.

By reallocating resources, Andrews was able to organize large offshore convoys with destroyers and escort vessels from the U. S. Atlantic Fleet and new construction. The first of the regularly scheduled coastal convoys departed on May 14.

Deprived of their sitting ducks along the Eastern Seaboard, Dönitz shifted his wolf packs southward into the Gulf of Mexico, Panama, and as far as Rio de Janeiro. The Gray Wolves found successful hunting grounds there, but it only delayed the inevitable. As the convoy system was extended to Rio in July, the U. S.

Navy sank more U-boats than it had in the entire war thus far. It was clear that what Dönitz’s submariners had come to call the “Second Happy Time” was finally over. He began transferring his U-boats back to the North Atlantic for a renewed onslaught on Allied convoys heading for Britain. Operation Drum Beat was a victory for Dönitz’s Gray Wolves and a disaster for the Allies.

During the first half of 1942, more than 360 merchant ships and tankers, totaling well over two million gross tons, were sunk in coastal waters from Canada to the Caribbean. More than 5,000 people died, the vast majority of them merchant seamen. Most of the blame lay with a single, hard-drinking, stubborn admiral.