On a sunny afternoon more than 75 years ago, Germany’s bloody U-boat campaign along the East Coast of the United States — which had resulted in the destruction of more than 200 Allied merchant ships and the deaths of thousands of civilians —abruptly ended with a rare defeat at the hands of the U.S. Navy.

The last skirmish in the U-boat offensive had begun just after sunset on July 11, 1942, when lookouts perched atop the narrow bridge of U-576 caught the distant silhouette of a group of merchant ships off to the west in the direction of Cape Hatteras, North Carolina.

Capt. Hans-Dieter Heinicke, the commander of U-576, quietly ordered his 44-man crew to battle stations. Heinicke began to trail the northbound Convoy KN118, sailing from Key West, Florida, to Norfolk, Virginia. He ordered his senior radioman to send an encrypted message announcing the sighting to the U-boat force headquarters (Befeblisheber der Unterseeboote, or BdU) in Paris.

As the western sky darkened, its operations staff tersely ordered Heinicke “to attack and to report further contact” so that other U-boats could be directed to close in on the formation.

Within several hours, U-402, another Type VIIC U-boat, arrived in the area.

Both Heinicke and Kapitänleutnant (Lt. Cmdr.) Siegfried Freiherr von Forstner, U-402’s skipper, were experienced and capable U-boat commanders with adequate records of ship sinkings.

Heinicke was on his fifth wartime patrol, hoping to add to his record of three ships sunk (totaling 13,387 gross registered tons).

Von Forstner’s record was nearly as impressive: In four wartime patrols, he had sunk three ships (totaling 11,135 tons).

Both were on their second deployment to American coastal waters since the beginning of the U-boat offensive. But as they hunted the elusive convoy during the next three days, their combat experience would prove to be of no use.

Except for a heavily armed convoy passing through every three days or so, the once rich hunting grounds off North Carolina’s Outer Banks were now empty of merchant ships.

And the skies were constantly swarming with land-based patrol aircraft.

Two days after Heinicke sighted Convoy KN118, two U.S. Navy patrol aircraft jumped U-576 while it was on the surface, straddling it with depth charges that damaged one of its main ballast tanks. Attempts to repair the tanks the next day were unsuccessful, prompting Heinicke to abort his patrol and begin the long return trip to France.

U-402 ran out of luck the following day, July 14, when a pair of Coast Guard aircraft blasted it with depth charges as it, too, attempted a crash-dive to safety.

Forstner reported to BdU headquarters that the attack had caused a battery explosion and other damage, forcing him to abort his patrol as well. Then, on July 15, as U-576 was proceeding east into the open Atlantic, Heinicke’s lookouts spotted another formation of merchant ships.

This was southbound Convoy KS520 heading from Hampton Roads to Key West. It comprised 19 merchant ships escorted by seven American warships: the old four-stack destroyers Ellis and McCormick, the 165-foot Coast Guard cutter Triton, the corvette Spry, and three smaller patrol craft.

Despite the damage to his boat, Heinicke decided to attack, firing a spread of four torpedoes. One struck and sank the 2,063-ton Nicaraguan freighter Bluefields; two others damaged the 8,310-ton American freighter Chilore and the 11,147-ton Panamanian-flag tanker J. A. Mowinckel.

Although successful, the bold attack proved fatal for Heinicke and his men. When compressed-air charges expelled the four torpedoes from the bow tubes, U-576 became unstable and popped to the surface in the middle of the convoy.

The defenders reacted instantly. A navy gun crew on the American freighter Unicoi struck the U-boat’s conning tower with at least one 5-inch shell, and two navy OS2U Kingfisher floatplanes swooped in and dropped depth charges that ripped open its hull.

U-576 sank within seconds, entombing its 45 crewmen on the seabed 721 feet down.

The six-month German submarine campaign against allied merchant shipping along the East Coast — Operation Paukenschlag (“Operation Drumbeat”) — had begun on Jan. 11, 1942.

First blood went to the Type IXB U-123, which torpedoed and sank the 9,076-ton British freighter Cyclops 326 nautical miles east of Boston.

During that period, 117 German U-boats carried out 168 patrols in North American coastal waters from Newfoundland to the Florida Straits.

They sank 240 Allied merchant vessels and escort warships for a loss of 1.25 million gross registered tons of critically needed petroleum products, armaments and ammunition, raw materials, and food.

A parallel U-boat offensive in the Caribbean and Gulf of Mexico that opened on Feb. 16 reaped nearly identical results, with 234 ships sunk for a loss of another 1.12 million gross registered tons.

The casualties were horrific: More than 6,800 Allied merchant sailors, naval gunners, and civilian passengers perished.

The U-boat force, on the other hand, lost only five boats through June 1942.

German submarine commanders called it the “American shooting season” because they were able to inflict so much damage with so little risk.

But in just two weeks — from June 30 to July 15 — the tide suddenly turned. The Allies sank an unprecedented seven U-boats, including three along the East Coast alone, and heavily damaged several others.

On July 19 German Adm. Karl Dönitz called off the East Coast offensive. (The Caribbean offensive would continue until September.)

He ordered the last two U-boats near Cape Hatteras to shift their patrol areas to waters off Newfoundland. Both Dönitz and the U.S. Navy’s Eastern Sea Frontier (ESF) headquarters agreed on why this phase of the Battle of the Atlantic was finally over.

After months of dithering and delay, the U.S. Atlantic Fleet had finally scraped together enough older destroyers, Coast Guard cutters, and other armed escort craft to implement an effective coastal convoy system between Key West and Hampton Roads and a second leg between Hampton Roads and New York. Other convoy routes within the Gulf of Mexico — and others linking New York and Boston and Boston and Halifax, Nova Scotia — would be added later.

The U-boat offensive was ultimately thwarted by a relatively small number of warships. Each escort group consisted of two destroyers, a Coast Guard cutter, and four smaller patrol craft, for a total of approximately 14 destroyers and 35 of the smaller escort vessels organized in seven groups.

“The increasing success of the past weeks rests on a solid basis of strong [defensive] forces properly used,” American Lt. Elting E. Morison later wrote in the Eastern Sea Frontier War Diary’s July 1942 edition.

For three-quarters of a century, the accepted narrative of the Battle of the Atlantic during the first half of 1942 has been straightforward: The Japanese attack on Pearl Harbor and declaration of war by Nazi Germany caught the U.S. Navy unprepared for a two-ocean war.

By December 1941 a majority of the Atlantic Fleet destroyers were fully committed to escorting transatlantic convoys between Newfoundland and Iceland, while others were assigned to the Caribbean, Gulf of Mexico, and South Atlantic. Still other destroyers were tied down serving as escorts for aircraft carriers and battleships.

Further diminishing the Atlantic Fleet roster, in the frantic weeks after Pearl Harbor the Navy had no choice but to transfer three battleships and an aircraft carrier from the Atlantic to offset the losses at Oahu, taking an additional 11 destroyers with them.

Allied merchant ships passing up and down the coast had to fend for themselves. The stage was set for a massacre.

Wartime navy leaders, postwar naval historians, and journalists generally held to that account for nearly a half century.

But as a steady flow of top-secret files have been declassified, researchers have discovered a much darker version of events surrounding the U.S. Navy’s response to Germany’s U-boat offensive.

The U-Boat offensive didn’t take the U.S. Navy by surprise.

Early on, the British were providing navy officials in Washington with explicit, detailed intelligence on the location and movement of not only the initial force of five U-boats but also the nearly two dozen more that made up the second wave of attackers.

British code-breakers had penetrated the U-boat force’s encrypted communications earlier in 1941 and, with the help of a robust network of radio direction finding stations across the North Atlantic, were able to triangulate the location of each U-boat at sea as it transmitted high-frequency Morse code messages.

Beginning in December 1941, the British Admiralty had forwarded daily “U-boat Situation Reports” to navy headquarters in Washington. The bulletin for Monday, Jan. 12, could not have been clearer in its warning:

The general situation is now somewhat clearer and the most striking feature is a heavy concentration [of U-boats] off the North American seaboard from New York to Cape Race [at the southern tip of Greenland]. Two groups have so far been formed. One, of six U-boats, is already in position off Cape Race and St. John’s [Newfoundland], and a second, of five U-boats, is apparently approaching the American coast between New York and Portland [Maine]. It is known that a total of 21 boats [are] heading west.

Reacting to that warning in the early hours of January 13, the staff at Navy headquarters alerted all major Atlantic Fleet commands to the approaching U-boats, even passing on their individual positions as provided in the Admiralty message. Thus, on the eve of Dönitz’s planned U-boat offensive, the U.S. Navy knew exactly how many U-boats were heading for the East Coast, their locations, and — by inference — their intentions.

The U.S. Navy also enjoyed a tactical advantage unprecedented in modern naval warfare — and had the means to exploit it. On the same day that navy headquarters dispatched the U-boat warning, Adm. Royal E. Ingersoll, the commander of the Atlantic Fleet, was assembling a powerful task force at Staten Island, New York, that totaled 23 Atlantic Fleet warships, including a battleship, an aircraft carrier, three heavy cruisers, and 18 front line destroyers.

But instead of organizing the destroyers at Staten Island into convoy escort groups to shield Allied merchant ships, Atlantic Fleet headquarters sent the task force on an entirely different mission: escorting a convoy of four troopships with a token force of 4,600 U.S. Army soldiers to Iceland and Northern Ireland.

The decision by top navy admirals to press on with this symbolic show of force despite the imminent U-boat attacks stripped the Atlantic coast of any effective defenses. When the five U-boats assigned to the initial attack began hunting targets in earnest late in the week of Jan. 11, their commanders were stunned by what they found: coastal sea-lanes teeming with merchant vessels sailing independently and without escort; few patrol aircraft and no U.S. Navy warships patrolling the littorals; and their targets brightly silhouetted by the lights from coastal cities and seaports.

At “Navy Main,” the three-story headquarters building on Constitution Avenue in Washington, D.C., the four weeks separating Pearl Harbor and the eruption of U-boat attacks offshore had indeed been a time of confusion, uncertainty, and near-paralysis.

The embattled staff had to cope with not only the destruction on Oahu but also a daily torrent of bad news from the Pacific. In less than four weeks after December 7, the Japanese invaded the Philippines, Wake Island, Guam, Malaya, the Dutch East Indies, Thailand, Burma, Hong Kong and Shanghai.

Making things even more uncertain, President Franklin D. Roosevelt and Navy Secretary Frank Knox had ordered a widespread leadership change for the sea service.

In addition to replacing Pacific Fleet commander Adm. Husband E. Kimmel with Adm. Chester W. Nimitz, FDR and Knox sidelined Chief of Naval Operations Adm. Harold “Betty” Stark with an assignment as commander of U.S. Naval Forces in Europe and named Atlantic Fleet Commander Adm. Ernest J. King as the new commander in chief to replace him.

Rear Adm. Royal Ingersoll, Stark’s assistant, in turn jumped two ranks and relieved King as head of the Atlantic Fleet.

The North Atlantic Coastal Sea Frontier, soon to be expanded and renamed the Eastern Sea Frontier, was responsible for defending the East Coast.

Commanded by Vice Adm. Adolphus A. Andrews and with its headquarters at the federal building in lower Manhattan, ESF, with few ships or aircraft of its own, had to rely on the Atlantic Fleet for any warships or patrol aircraft.

As New Year’s Day dawned, King, Ingersoll, and Andrews — working from Washington, Norfolk, and New York — had no time to organize and execute an effective defense.

King would later recall entering his new office in late December and glumly surveying the barren office and shabby flat-top desk he had inherited.

“Nothing was ready,” King later recalled. “I had to start with nothing.”

When King formally became commander in chief on December 30, 1941, and Ingersoll raised his four-star flag in Norfolk two days later, the leading U-boats for Operation Drumbeat had already crossed 047 degrees West Longitude, due south of Cape Race, Newfoundland, and were closing in on their target areas.

King, in particular, knew that the navy needed to organize convoys to protect the merchant ships traveling up and down the East Coast. Like many other senior navy officers who had served in World War I, King knew only too well how German U-boats had come close to strangling the British economy in 1917 and 1918 before a robust convoy system saved the day.

Then-Royal Navy Cmdr. Peter W. Gretton, a seasoned British convoy escort commander, described the effectiveness of convoying in simple and clear terms: “Convoy is the essence of offense, for instead of dispersing your forces in search of an enemy whose object is to avoid them, it forces the enemy to scatter his forces in search of your shipping, and when he finds it, either to fight on your own ground and on your own terms in order to reach your shipping, or to remain impotent.”

King would echo that assertion in a letter to Gen. George C. Marshall, the U.S. Army’s chief of staff, on June 21, 1942, at the height of the U-boat offensive: “Escort is not just one way of handling the submarine menace; it is the only way that gives any promise of success.”

In addition to his strong views on the subject, King had long lobbied effectively for more antisubmarine warships. Three years before rising to commander in chief, King, as a member of the Navy’s General Board, had pressed for the mass production of convoy escort ships modeled after the seven Treasury-­class Coast Guard cutters already in service, whose range and armament made them excellent U-boat hunters.

Appointed to command the newly reactivated Atlantic Fleet in February 1941, King had presided over the construction of navy bases in Newfoundland and Bermuda and had carried out FDR’s orders to have Atlantic Fleet destroyers secretly join in the escort of transatlantic convoys beginning on Sept. 1, 1941, with Convoy HX150.

On his watch, the fleet found itself by the late summer of 1941 in an undeclared shooting war with the U-boats, culminating with the damaging of the destroyer Kearny by U-568 on Oct. 17 and the Oct. 31 sinking of the destroyer Reuben James as it escorted eastbound Convoy HX156.

On Nov. 17, 1941, King wrote Vice Adm. Andrews at ESF headquarters: “It seems to me that the time is near at hand when we shall have to begin to make up our own convoys at Boston, New York, Hampton Roads …. Each of these posts requires an organization to deal with the make-up of convoys, such as that now in force at Halifax and at Sydney, Nova Scotia.”

Less than four weeks later, in mid-December, King wrote Chief of Naval Operations Stark to bemoan the “weakness of our coastal defense force” and to urge that the Navy prepare for the “imminent probability of a [German] submarine attack” in American coastal waters.

The shifting strategic situation, King added, “make[s] it essential that the maximum practicable number of our destroyers be based at home bases.”

His proposal went nowhere. The U.S. Atlantic Fleet already had its hands full.

On Dec. 7, 1941, the Atlantic Fleet destroyer force was large enough — at least on paper — to deal with the impending U-boat threat.

But two factors cut deeply into that capability.

First, the destroyers were being worked hard at other tasks that precluded them from being redeployed to guard the East Coast. At that juncture, there were 107 U.S. Navy destroyers plus six Treasury-class Coast Guard cutters in the Atlantic Fleet, for a total of 113 warships.

A month later, after the last of them left for the Pacific, there were 102. Of those, only 71 were fully operational: nine new destroyers were awaiting formal commissioning; another 12 were still carrying out post-commissioning workups, and another 10 were in shipyards for repairs.

More than three-fourths of the operational fleet — 53 destroyers and three of the large cutters — were assigned to Rear Adm. Arthur L. Bristol’s Task Force 24. Their mission was to escort eastbound HX convoys staging out of Halifax, Nova Scotia, from the rendezvous south of Newfoundland to a “mid-ocean meeting point” south of Iceland, where British warships then shepherded them the rest of the way to the United Kingdom.

Task Force 24 and the Canadian navy also shared responsibility for protecting westbound ON Convoys sailing the reverse route from the British Isles to North America, escorting them from the mid-ocean meeting point to dispersal locations in the western Atlantic where the merchant vessels would then proceed independently to their assigned ports of call.

The American escorts managed odd-numbered ON convoys and the Canadians even-numbered formations.

Further complicating the situation, by Jan. 12, nine of the 53 Task Force 24 destroyers were laid up for storm damage repair, with a 10th — the Benson-class Kearny — still under repair after its October encounter with U-568.

Of the remaining 25 destroyers, 14 were operating in the Caribbean and South Atlantic, eight were assigned as escorts (four apiece) to the carriers Wasp and Ranger, and three were preparing for a patrol mission to Bermuda.

A second factor restricting any major diversion of Atlantic Fleet destroyers concerned the two general categories of the ships in the destroyer force in early 1942.

There were 43 front line warships in seven modern classes. These had been commissioned between 1936 and 1941.

Another 31 were older four-stack destroyers commissioned between 1918 and 1921, whose limited range hampered convoying and whose poor hull design made them less maneuverable than the newer warships.

When the Atlantic Fleet began escorting convoys in secret in September 1941, King and Bristol balanced out each group with at least two front line destroyers and three or four of the old four-stack models.

Once in the U.S. Navy’s top position, King had the power and authority to carry out the urgent defensive realignments against the U-boat threat that just weeks earlier he had advocated as commander of the Atlantic Fleet.

But an urgent meeting in Washington, D.C., between Roose­velt and British prime minister Winston Churchill, with senior military and political advisers on both sides, soon prevented that shift.

Just after the United States entered the war, Churchill pressed FDR for a face-to-face meeting to hammer out a joint strategy for upcoming military operations. Crossing the North Atlantic on the British battleship Duke of York, the British delegation met with their American counterparts beginning on Dec. 22 in what was later called the Arcadia Conference.

It would become a three-week marathon of decision making. Topics included the “Germany first” priority for fighting the Axis; organizing the Anglo-American Combined Chiefs of Staff for overall military leadership; devising a strategy to halt Japanese advances in the Far East; and planning future Allied expeditions in Africa and Europe.

One item on the Arcadia agenda would, in the end, make the formation of a coastal convoy system impossible.

A top British priority was Churchill’s desire to immediately transfer some 25,000 British troops from Iceland and Northern Ireland to North Africa or the Far East and to replace them with U.S. Army soldiers. While crossing the Atlantic, Churchill dictated a memorandum for the upcoming conference in which he argued that the presence of three U.S. Army infantry divisions and one armored division in Northern Ireland “would be a powerful additional deterrent against an attempt at invasion [of the British Isles] by Germany” and would also enable the British Army to reinforce its campaign in North Africa.

Roosevelt and his top military aides had in fact been discussing the idea of an Iceland troop swap with the British for several months. At Arcadia, Roosevelt made no secret of his desire to get the United States into the war against Germany as quickly as possible to show support for the embattled Soviet Union as well as to shore up civilian morale at home and in the United Kingdom.

Sending troops to Iceland and Northern Ireland would be an effective first step. In addition to the Iceland–Northern Ireland troop swap, FDR supported the British proposal for an Anglo-­American invasion of Northwest Africa (Operation Gymnast) later in 1942.

If either King or Marshall had doubts about sending soldiers to Iceland — which would also allow the return to the United States of a provisional regiment of 4,095 Marines that had joined the British troops on Iceland five months earlier on July 7, 1941 — no objections were entered in the official conference record.

On Jan. 5, 1942, his sixth day as commander in chief, King co-signed with Marshall a six-page “Joint Army and Navy Directive” on implementing the decision to send the troops to Iceland.

The operation would begin on Jan. 15 with the sailing from New York of Convoy AT10, consisting of 10 troopships carrying 8,000 soldiers from the 5th Infantry Division to Iceland, and another 14,000 troops from the 34th Infantry Division as the vanguard for the four divisions that Churchill wanted in Northern Ireland.

Then the plan encountered the fog and friction of war. King and Marshall found themselves confronted by other, equally urgent requests for American soldiers. Over the 10 days between the issuance of the King-Marshall memorandum and the convoy’s sailing date, the expeditionary force for Iceland and Northern Ireland radically shrank.

In the end, only 2,200 soldiers would sail for Iceland and another 2,400 would go to Northern Ireland. The other 17,400 soldiers had new orders to deploy to the southwest Pacific and Australia.

On January 5 King ordered Ingersoll to create Task Force 15 to escort the now much-reduced Convoy AT10.

Rear Adm. Alexander “Sandy” Sharp Jr. would lead the task force from his flagship, the battleship Texas. Also joining the force were the aircraft carrier Wasp; heavy cruisers Quincy, Tuscaloosa, and Wichita; and 18 front line destroyers.

Ingersoll had no choice but to raid the transatlantic convoy escort force of 14 destroyers. The four Norfolk-based escorts to the carrier Wasp brought the total number of destroyers to 18.

Task Force 15 would provide Convoy AT10 with an impenetrable ring of escort warships as it crossed the North Atlantic. Its departure also stripped the U.S. East Coast of the last front line destroyers positioned and equipped to meet the U-boat threat.

The leading U-boats in Operation Drumbeat and the 27 ships in the combined troop convoy and task force passed each other without contact on Jan. 15, 1942, but there was one near-miss. Lt. Cmdr. Reinhard Hardegen, the skipper of U-123, was heading east about 30 nautical miles south of Southampton, New York, at 3 a.m. when his lookouts spotted the navigation lights of a large oil tanker coming up fast behind them, its massive hull silhouetted by the distant glow of lights from Long Island.

Maneuvering for a point-blank shot, Hardegen fired a single G7e electric torpedo, which struck the 6,768-ton British tanker Coimbra on the starboard side just aft of its amidships superstructure.

The torpedo detonation set up a towering explosion that lit up the night sky. Flaming lubricating oil from its cargo tanks rained on the stricken ship, which within minutes was engulfed in fire bright enough to be seen by residents along the Long Island shoreline, just 27 nautical miles away.

Eighteen minutes later, Hardegen fired a coup de grâce that struck under Coimbra’s funnel and sent it sternfirst to the seabed 175 feet down, with its bow bobbing on the surface.

Nine hours later, the carrier Wasp and four destroyers were proceeding north from Hampton Roads to rendezvous with Task Force 15 when, at 35 minutes past noon, lookouts on the destroyer Mayrant sighted a shipwreck bearing nearly due north.

Breaking off formation with the carrier, Mayrant and Rowan maneuvered into a large oil slick, where they helped to rescue 10 survivors from the Coimbra’s 46-man crew.

The officer of the deck on Mayrant, Lieutenant j.g. Franklin D. Roosevelt Jr., dutifully recorded the two-hour rescue in the ship’s deck log as the two destroyers retrieved the sodden tanker crewmen.

While the two destroyers were maneuvering to pull the Coimbra survivors from the water, at 2 p.m., 74 nautical miles away, the troopships Munargo, Borinquen, Chateau Thierry, and Straithaird were casting off from the pier at Brooklyn Naval Shipyard to begin heading down-channel toward the open Atlantic.

Meeting the initial contingent of Task Force 15, they formed three columns of two ships apiece, with Iceland-bound Munargo and Borinquen in column one to starboard, the battleship Texas and heavy cruiser Quincy in the middle in column two, and Belfast-bound Chateau Thierry and Straithaird to port in column three.

By the next day, the formation was heading east-­southeast for its initial routing waypoint, with six of the 18 assigned destroyers steaming in a protective screen, and four more encircling the Wasp. At that juncture, the convoy and its escorts were joined by four more destroyers out of Argentina, Newfoundland, and the convoy set on a new base course for the mid-ocean meeting point south of Iceland.

This was actually a smaller escort formation than Ingersoll had intended: Through a miscommunication, five destroyers from Casco Bay, Maine, assigned to be part of Task Force 15 missed the original rendezvous on Jan. 16 when they were not informed that the meeting point had been shifted about 100 miles north.

Four of the five destroyers were able to accompany Convoy AT10 for six hours on Jan. 19 but then turned back to New York, where they were reassigned to a new convoy screen, Task Force 16.

This group of escorts was charged with escorting seven troopships and six fast minelayers (ex-destroyers) bound from New York to Australia via the Caribbean, Panama Canal, and Pacific Ocean.

That assignment kept them occupied throughout January. Meanwhile, the rest of Task Force 15 escorted Convoy AT10 to the mid-ocean meeting point, where three British destroyers joined the two Belfast-bound troopships, and the other two proceeded north to Reykjavik, Iceland, arriving on Jan. 25.

The U.S. Navy’s decision to press ahead with the Jan. 15 sailing of Convoy AT10 with the task force that included 18 front line destroyers was a major factor in the fatal weakening of defenses against the U-boats along the East Coast.

But another factor contributed to the disaster. Despite the soaring ship losses in the weeks and months that followed, King and Ingersoll doggedly stuck to the plan first unveiled at the Arcadia Conference to organize monthly troop convoys protected by large escort formations.

Two of the cruisers and six destroyers that had escorted the two troopships to Iceland brought them back to New York as Convoy TA10, arriving on Feb. 9. And a week after that, Convoy AT12, comprising 15 troopships carrying 10,300 soldiers, left New York for Belfast on Feb. 19.

Among its 17 escorts were nine destroyers that had sailed with Task Force 15 a month earlier. Each one of those troopship formations required between eight and 10 Atlantic Fleet destroyers.

Why did King and Ingersoll proceed with Convoy AT10, knowing that it would leave the East Coast of the United States totally defenseless?

Even a cursory examination of the Atlantic Fleet destroyer list for January 1942 shows that enough front line destroyers were available — from Task Force 15 alone — to form six or seven coastal escort groups.

Alas, a comprehensive search of the commander in chief and the chief of naval operations archives from that era reveals nothing that suggests the admirals ever questioned or debated with their civilian superiors the probable cost in Allied shipping if the East Coast were stripped of effective escort warships. In contrast, the result of that decision is well known: a maritime slaughter.

Did the Allied leaders learn from their decision to strip the Atlantic seaboard of antisubmarine defenses even though they knew the U-boats were on their way?


Eight months after withdrawing from American coastal waters in July 1942, the U-boat force had grown significantly.

On New Year’s Day 1942, Adm. Dönitz had just 50 operational U-boats in the Atlantic.

By March 1943 the number had reached 114, giving U-boat force headquarters the ability to organize “wolfpacks” of up to two dozen U-boats to conduct mass attacks against Allied convoys in the North Atlantic.

When 32 U-boats in a pair of wolfpacks sank 21 merchant ships from eastbound Convoys HX229 and SC122 in mid-March, naval leaders in Washington and London feared that the U-boats were on the verge of overwhelming the North Atlantic convoy escorts.

In response, Churchill canceled sailings of the Iceland–Murmansk convoys for six months and redeployed several dozen British destroyers to the North Atlantic to serve as “support groups” available to aid convoys under attack.

Within two months, the Allies decisively routed the Germans in a series of bloody convoy battles, and Dönitz was forced to withdraw Germany’s U-boats from the North Atlantic.

Ed Offley authored two books on the Battle of the Atlantic, including Turning the Tide: How a Small Group of Allied Sailors Defeated the U-boats and Won the Battle of the Atlantic (Basic Books, 2011) and The Burning Shore: How Hitler’s U-boats Brought World War II to America (Basic Books, 2014). This article initially appeared in the Winter 2018 issue (Vol. 30, No. 2) of MHQ—The Quarterly Journal of Military History with the headline: Undefended Shore. MHQ is a sister publication of Navy Times. Subscribe now at special savings!

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