Fighting the U-boats
Allied Navies

US Navy –
Tenth Fleet Fights the U-boats


Tenth Fleet was a unique organization within the United States Navy; never before or since WW II did an organization like Tenth Fleet exist. Under the personal command of the Navy’s top sailor, Fleet Admiral Ernest J. King, this fleet, created expressly to fight the U-boats, never put to sea (it had no ships) and never had more than about 50 people in its organization, all of whom fought the U-boats with remarkable results from their desks in the old Navy Department building on Constitution Ave. in Washington DC. Tenth Fleet did not exist at the start of the war between Germany and the United States, and had its origins largely in the Allied disaster which took place off the east coast of the United States in 1942. In May of 1943, Tenth Fleet had control over all aspects of the US Navy’s battle against the U-boats in the Atlantic but by the end of June 1945 no longer existed.

Operation Paukenschlag – U-boats off the East Coast of the U.S.

When Admiral Doenitz launched Operation Paukenschlag in December of 1941, the five U-boats (U-125, U-123, U-66, U-130, U-109) of the initial wave sent against the United States found the east coast, for all practical purposes, un-defended. Admiral Andrews commanding Eastern Sea Frontier, had at his disposal:

  • 4 Yard Patrol Boats
  • 4 Subchasers
  • 1 Coast Guard Cutter
  • 3 WW I “Eagle” boats
  • 103 aircraft, five of which were combat ready

This tiny force was to protect a 28,000 sq. mile area extending from the St. Lawrence River down to North Carolina. Defense forces in the Gulf of Mexico and the Caribbean were in no better shape.

The Paukenschlag boats arriving on the United States east coast in January 1942 found the merchant fleet sailing unescorted and with lights on at night. There was no radio discipline; ship and shore stations operated as if in peace time, broadcasting time signals and weather reports. Shoreside cities blazed with lights at night. The U-boats, hardly believing the bonanza offered them, rampaged up and down the coast with impunity, sinking everything in sight. Operation Paukenschlag lasted but 10 days, during which 25 ships totaling about 200,000 tons were sunk. Not a U-boat was damaged much less sunk. Those five boats were only about 12 percent of the U-boats at sea but they accounted for 70 percent of the Allied shipping sunk in January 1942.

Ladislas Farago, in his book “The Tenth Fleet”, states the situation succinctly; In the next fifteen months, the United States was to suffer a defeat compared with which Pearl Harbor was but a slap on the wrist. The United States had entered the war ill-equipped to fight the U-boats in the Atlantic and the price was about to be paid for the failure to plan and prepare.

Paukenschlag was only the first taste of what was to come. The U-boat commanders vied for the chance to take part in the “American Shooting Season” as it was called in Germany. By the spring of 1942, the Allied shipping losses were so high in the American defense zone, British Prime Minister Winston Churchill was compelled to write President Roosevelt in March 1942, …I am most deeply concerned at the immense sinkings of tankers west of the fortieth meridian and in the Caribbean Sea…. Continuing on, Churchill writes, …The situation is so serious that drastic action of some kind is necessary… . In June 1942, the American Chief of Staff, General George C. Marshal wrote to Admiral King, …The losses by submarines off our Atlantic seaboard and in the Caribbean now threatens our entire war effort….

And as yet undeterred, the U-boats in 1942 continued to arrive in the Western Atlantic in steadily increasing numbers. 70 U-boats were off the east coast of the United States in July. This number increased to 86 in August, 100 in September, and 105 in October. A total of 524 ships were sunk in waters of the American defense zone between July and December 1942 and the onslaught continued unabated into the first three months of 1943. A record high of 7,697,905 tons of merchant shipping was sunk in all sectors of the Atlantic in 1942 at a cost of 86 U-boats sunk.

The magnitude of the disaster for the Allies, and in particular for the United States, is in the record. During the United States first year in the war, 1,027 Allied ships were lost to the U-boats, most of these in the American defense zone. This number represents more than half of all ships lost to the U-boats in the whole period of the war from 1939 to 1945.

Tenth Fleet is Born

By the end of 1941 the British Navy had developed North Atlantic convoy protection measures to the point where Admiral Doenitz found the cost of attacking the convoys too high in terms of U-boat losses and redeployed to the mid-Atlantic. But off the United States east coast, the sinkings continued at a high rate during 1942. It was against this background of submarine warfare in the Atlantic the American President and British Prime Minister met in Casablanca in January of 1943 to discuss issues of strategic importance and the conduct of the war in both the Atlantic and the Pacific. It was clearly recognized by the Allies that until such time as the sea lines of transport to England were made safe from the U-boats, the planned cross-channel invasion of Europe would be impossible. Significantly, the Combined Chiefs of Staff in their final report at Casablanca stated …the defeat of the U-boat must remain the first charge on the resources of the Allied Nations.

Admiral King fully supported this resolution and upon his return to Washington DC, began the planning and changes in the Navy which he considered necessary to defeat the U-boats. Realizing that a truly revolutionary approach to the problem was required, which could not be achieved by a mere reshuffle and polishing of current Naval forces and organizations, he set forth in a completely different direction.

One of his first steps was to return Capt. Francis Low to his staff. Low had been on Admiral King’s staff when King was appointed Commander in Chief US Navy in December of 1941. In September 1942 Low left Admiral King’s staff and went to sea in command of the cruiser Wichita. Recognizing he would not be able to personally devote all the time necessary to the planning and implementation of the organization he had in mind, Admiral King recalled Capt. Low to take on the job.

Low reported back to Admiral King in March 1943. Promoted to the rank of Rear Admiral and appointed Asst. Chief of Staff (Antisubmarine), Admiral Low’s first task was to prepare a plan which would bring together under one command all the antisubmarine elements of the US Navy. For the first time intelligence and operations were to be fully unified in one command

The initial plan, incorporating both Admiral King’s ideas and the results of an intensive study of both British and American navy antisubmarine organization, operational experience, tactics, and weapons, was ready within two months. Key features of the plan were:

• Primary objective to be the destruction of enemy submarines

• The new organization was to be commanded by the highest rank

• It would have no ships of its own but would have the power to commandeer whatever ships and aircraft were needed for the ASW effort.

• The organization was to be kept small in size but with access to all Navy agencies with especial focus on intelligence services.

• To be organized as a “fleet” to simplify personnel and administrative procedures, and to facilitate the use of fleet communications channels.

By May 1943 planning was well enough in hand for Admiral King to send the Joint Chiefs a message announcing It is arranged to set up immediately in the Navy Department an antisubmarine command to be known as Tenth Fleet. Admiral King appointed himself commander of Tenth Fleet with Admiral Low as his Chief of Staff, but for all practical purposes, Low ran Tenth Fleet. While having the authority to do so, Admiral Low never issued direct orders to the operational commanders. Instructions were issued in the form of “suggestions” or “recommendations”. But it was clearly understood by all hands these were in effect orders emanating directly from Admiral King and they were to be carried out swiftly and without question.

Tenth Fleet was staffed with about 50 people hand-picked for their training and expertise in the matters at hand. Housed in the Navy Department Bldg. in Washington DC, Tenth Fleet was organized around five operational sections:

1. The Civilian Scientific Council (ASWORG)

2. Convoy and Routing Division

3. Anti-Submarine Development Unit – Atlantic Fleet

4. Anti-Submarine Measures – Development Unit

5.  Operations Division

These five sections had oversight responsibility for and coordinated every facet of the US Navy Atlantic antisubmarine effort including the direction of operational forces, personnel training in antisubmarine warfare and tactics, new weapons development, at-sea evaluation and testing of new weapons and tactics, convoy routing and protection, and intelligence operations.

Early in the planning for Tenth Fleet, Admiral Low recognized a first-class intelligence operation was essential to Tenth Fleets operations; on the other hand there was neither the time or facilities available to establish a new intelligence group, nor, as it turned out, was such a step even necessary. Prior to the formation of Tenth Fleet, Admiral King had established the Combat Intelligence Division (CID) COMINCH which reported directly to him. Both Admirals King and Low agreed the Atlantic Section of CID would supply Tenth Fleets intelligence information requirements.

The importance of the intelligence operations carried out within the Combat Information Division, Atlantic Section cannot be overemphasized. Intelligence information was the lifeblood which transfused the whole operation and led to the ultimate success of Tenth Fleet. The information produced by the Atlantic Section influenced and guided the efforts of all the antisubmarine activities tended by Tenth Fleet and had a profound effect on the activities of the operational forces at sea and in the air.

Commander Kenneth Knowles was in charge of the Atlantic Section which concentrated its attentions on the U-boats. Knowles maintained a situation room, somewhat similar to that of his counterpart in the British Admiralty with whom he maintained close contact. Daily briefings were conducted in this room for Admiral Kings staff and the various operational commanders. A large map was maintained on which was plotted convoy positions, the forces at sea, and the U-boat positions. Knowles staff kept the plots up to date on a continual 24 hour basis.

The information from which the plots and operational analyses were made came from a number of sources. Information was freely exchanged with Cdr. Knowles counterparts in the British Admiralty. The British codebreakers at Bletchley Park had deciphered the Enigma codes and the Allies were reading the U-boat communications. Agents in Europe provided information on U-boat movements and dispositions. A string of high frequency direction finding stations, the “Huff-Duffs”, some 26 in all, were established extending from Lands End and the Shetlands in Britain to Iceland, Greenland, New-foundland, down the east coast of the United States, to Brazil, and in Africa. German submarine tactics required frequent radio transmissions between the U-boats at sea and Adm. Doenitz submarine headquarters. The U-boats, ringed by the Huff-Duffs, were in effect, and unknown to them, providing fixes on their positions at sea when they transmitted. All of this Cdr. Knowles had access to in making his operational analysis and Tenth Fleets “recommendations” to the fleet units.

Tenth Fleet Goes to War

The commencement of Tenth Fleet’s operations was officially announced 20 May 1943, only shortly after the arrival of the Bogue class escort carriers in the Atlantic. On May 22, 1943, VC-9 aircraft from USS Bogue, operating with information provided by Tenth Fleet, closed with and sank U-569. This was the first sinking of a U-boat in which Tenth Fleet had an active role; it was also the first U-boat to be sunk by Bogue.

While Tenth Fleet had responsibility for and provided assistance to all ASW operations, a special relationship developed with the escort carriers. Given their ability to move rapidly, sweep large areas of the ocean, and to stay on top of and pursue a contact for long periods of time, the escort carrier task groups were able to make effective use of the information provided by Tenth Fleet. So effective did this team relationship become, Admiral Ingersoll, Atlantic Fleet commander, for all practical purposes turned the operational control of the carriers over to Tenth Fleet.

On the morning of 13 July 1943, U-487 sent a radio transmission to Berlin. Tenth Fleet intercepted the transmission on the Huff-Duffs and fixed U-487’s position NW of the Cape Verde Islands. Within the hour, Tenth Fleet passed this information to Atlantic Fleet which relayed it to USS Core, operating in that area. Wildcats and Avengers from Core ran down the fix, found U-487 on the surface and sank her. Total elapsed time from U-487’s transmission to Berlin to her final position on the bottom – 10 hours. The carrier commanders were enthusiastic supporters of Tenth Fleets inputs to their operations.

In reality, the location and sinking of a submarine by a carrier task group was rarely, almost never, as simple as it might seem from this example. A position “fix” was an estimated position calculated by a triangulation process based on “bearings only” information supplied by the Huff-Duff stations. As in any measurement process, there was always an error in the calculated position and the error was highly variable depending on a number of factors related to the characteristics of radio transmissions over long distances. The difference between the submarines actual position and its calculated position could be anywhere from a few tens of miles to as much as a couple of hundred miles. A good “fix” might be one in which the U-boat was within 50 miles of the calculated position. At first this doesn’t sound like a significant problem. However, a 50 mile error in the “fix” meant the submarine could be anywhere within a circle of 50 miles radius. Such a circle contains about 8,000 square miles of open ocean the task group might have to search out. If the error were to double, say to 100 miles, the area to be searched in-creases by a factor of 4 to 32,000 square miles; a formidable problem. If the U-boat was moving, the area of uncertainty increased even more rapidly. Fortunately for the hunters, a series of position fixes obtained over a period of several days would usually vector the carrier groups in close enough so that they could establish local contact. Once a localized contact was obtained by the escort carrier group, the U-boat was in a very precarious situation. The following incident is a classic illustration of Tenth Fleet working with a Hunter-Killer group.

In March 1944 Tenth Fleet began tracking a solitary U-boat as it transited the Bay of Biscay departing Lorient on patrol. The U-boat was tracked over the next two month period as it moved south to a position off Portugese Guiana. US Navy Task Group 22.3 with Captain Daniel V. Gallery in USS Guadalcanal commanding had departed Norfolk on 15 May bound for the Cape Verde Islands on a routine sweep. On 27 May the carrier group and the U-boat were about 300 miles apart, neither aware of the others presence. On May 31 Guadalcanal was informed of the U-boats position and instructed to go after it. During the next 5 days Tenth Fleet continued to monitor the action and provide updated position fixes as the Task Group, conducting intense search operations, closed in.

On June 4, 1944 contact was gained on U-505, the boat forced to the surface, boarded, and taken under tow. Without Tenth Fleets participation it is highly unlikely this famous incident would ever have taken place.

Tenth Fleet’s operations proved highly effective. In the 18 month period prior to May 1943 when Tenth Fleet began operations, all US forces sank 36 U-boats; in the following 6 month period 65 U-boats were sunk.

Tenth Fleet is best remembered for its association with the escort carrier hunter-killer groups. However, this organization supported all the fleet units involved in ASW operations, including the land based patrol aircraft, participating in actions which resulted in the sinking of 101 U-boats. Held secret during the war, the existence of Tenth Fleet and its inputs to the fleets operational units were unknown to the crews aboard the ships and aircraft fighting the U-boats at sea, except for a few select people. After the surrender of Germany in May 1945, Tenth Fleet was disbanded, personnel re-assigned, and by the end of June was no longer in existence.


  • Twenty Million Tons Under the Sea
    Rear Admiral Daniel V. Gallery
    Henry Regnery Co., Chicago
  • Hunter-Killer
    William T. Y’Blood
    Naval Institute Press, Annapolis
  • The Tenth Fleet
    Ladislas Farago
    Richardson & Steirman, New York
  • The Atlantic Campaign
    Dan van der Vat
    Harper & Row, New York