Fighting the U-boats

Aircraft & Air Forces

American Air Forces

The Battle against the U-boat in the American Theater

December 7, 1941 - September 2, 1945



Only five ships had been sunk in the Gulf Sea Frontier in the first four months of 1942, but in May 1942, submarines sank 41 ships, totaling 219,867 gross tons, with 55 percent tanker tonnage. By July 1942, the enemy had sunk 62 ships in the Gulf of Mexico. As many as four enemy submarines at a time prowled the Gulf of Mexico between May and August 1942, taking advantage of skimpy air patrols and the lack of a convoy system.

The shift of the German submarine offensive to the Gulf overwhelmed the resources of the U.S. Navy and the USAAF, which were barely adequate to defend against submarines in the Eastern Sea Frontier. The U.S. Navy had created the Gulf Sea Frontier in February 1942 with minimal surface and air forces, and the USAAF had contributed only 14 observation aircraft and two worn out B-18's. To counter increased submarine attacks, the USAAF, between 8 and 10 May, sent a squadron of light bombers (A-29's) to Jacksonville, Florida, and six medium bombers (B-25's) to Miami, Florida and on 20-21 May sent a detachment of B-25's to Havana, Cuba, to patrol the Yucatan Channel.

Admiral Doenitz
On 26 May, the 1st Air Force created the Gulf Task Force and stationed it at Miami. This organization, which continued to operate until November 1942, cooperated with the Commander, Gulf Sea Frontier, to provide operational control of all USAAF aircraft that flew anti submarine patrols in the area. At the end of July 1942 the U.S. Navy instituted a convoy system in the Gulf of Mexico, and German submarines faced the same dangers they had off the East Coast. On 4 September 1942, the United States lost the last ship sunk by enemy action in the Gulf of Mexico, as Admiral Doenitz withdrew all submarines from the Gulf.

The devastation of German submarine attacks in the Caribbean Sea Frontier matched that in the Gulf Sea Frontier. Having dispatched a sizeable force to the U.S. East Coast, Admiral Doenitz fixed the opening of the Caribbean operation for the new moon period of February 1942. On 16 February, a German submarine sank two tankers off San Nicholas, Aruba, then moved into the harbor and shelled a refinery, inflicting little damage but killing four people. In February and March, the Germans operated six submarines in the Caribbean Sea, each patrolling for two to three weeks before returning to France. Then, in April, a second wave of submarines arrived in the area; some, refueled and replenished northeast of Bermuda by "milch cow" submarines, stayed up to six weeks. By July, the German submarines had sunk some 141 ships and sank another 173 ships in the Caribbean Sea Frontier and its approaches by September. Between February and September, the German submarines sank an average of 1.5 ships each day, destroying over one million gross tons in the Caribbean and adjacent waters.

U.S. military leaders had been aware of possible threats in the Caribbean and the Gulf of Mexico at the beginning of the war. The USAAF, fearing an attack on the Panama Canal, in December 1941 transferred to the Canal Zone 80 additional fighter aircraft, nine heavy bombers, and four mobile radar sets. In February 1942, the 6th Air Force assumed responsibility for the aerial defense of the Panama Canal. Major General Davenport Johnson, Commander General 6th Air Force, concentrated aerial patrols on the Pacific side in fear of a carrier borne Japanese attack. Then in April 1942, when the German submarine threat became evident, the 6th Air Force, cooperating with the U.S. Navy, instituted anti submarine patrol flights as far east as Curacao. Most flights were by tactical aircraft, such as Bell P-39 Airacobra’s and Northrup A17's, which could fly only during daylight; lacking radar and trained observers, the pilots had little luck in spotting enemy submarines. On the other hand, 6th Air Force aircraft occasionally attacked friendly ships and submarines, fortunately without damaging them.

The USAAF in February 1942 organized a provisional force, later designated the Antilles Air Task Force. Scattered about the Caribbean in Trinidad, Curacao, Aruba, St. Lucia, Surinam, British Guiana, Puerto Rico, St. Croix, and Antigua, it consisted of about 40 B-18 medium bombers, seven Douglas A20 Havoc light bombers, and several fighter aircraft. Although remaining substantially the same size through the year, the task force obtained radar equipped aircraft, vastly increasing its anti submarine capability. Prior to July the air crews reported few sightings of or attacks on submarines, but in July and August attacked 20. To supplement these efforts, the 1st Air Force sent six B-18's equipped with radar to the Caribbean Sea Frontier. This unit, shuffled from one island and commander to another from August to November 1942, accomplished little.

The U.S. Navy extended the convoy system to the Caribbean Sea Frontier, with the first convoy sailing on 10 July 1942, between Guantanamo, Cuba, and the Canal Zone. In reaction, Admiral Doenitz redeployed his submarines to the Trinidad area where targets were lucrative and relatively unprotected. In August, the submarines sank only one ship in the rest of the Caribbean while destroying ten near Trinidad. Because of the extensive Caribbean air patrols, the submarines attacked independently, continuing their success into September, sinking an additional 29 ships totaling 143,000 tons.

The USAAF stationed detachments of B-18's at Trinidad, Curacao, Dutch Guiana, and British Guiana in June 1942; but these aircraft, lacking radar, could not stem the German efforts in the area during July and August. On 17 August, to aid the Caribbean Sea Frontier, the USAAF sent a detachment of B-18's equipped with microwave radar to Key West, Florida. The detachment, which always patrolled the Trinidad area, moved to other bases in the Caribbean and was based at Trinidad between 22 September and 16 October 1942.


OCTOBER 1942 - AUGUST 1943

By October 1942, the USAAF had been engaged in anti submarine war for almost a year. During that time it had laid the basis for an effective organization and made plans for a larger anti submarine force. To take advantage of these plans, the USAAF on 15 October 1942, activated the US Army Air Forces anti submarine Command (AAFAC) to replace I Bomber Command, which held most of the USAAF's anti submarine resources. I Bomber Command furnished the personnel, aircraft, and equipment for the new organization, which remained under U.S. Navy operational control. The AAFAC provided a greater unity of command of anti submarine forces in the War Department, resulting in increased flexibility and more effective operations. The I Bomber Command had been handicapped in its efforts because its primary mission remained longrange bombardment. The anti submarine task was secondary and presumably temporary. "Now," in the words of the official history of the USAAF in World War II, "as an officially constituted anti submarine unit, the AAFAC was able to attack its problems with undivided energy, free at least from any immediate uncertainty as to its mission." The reorganization extended to subordinate elements as well. By 20 November 1942, the AAFAC had organized the squadrons it had inherited from I Bomber Command into the 25th and 26th anti submarine Wings with headquarters at New York and Miami respectively.

In January 1943, the command had only 19 squadrons and only 20 B-24's, the aircraft type most useful for long range anti submarine patrolling. The command grew rapidly until, by September 1943, there were 25 anti submarine squadrons, most of which flew B-24's modified for anti submarine war. At the end of 1942, most of these squadrons operated in the Gulf, Caribbean, and Eastern Sea Frontiers on endless patrols with few sightings and fewer attacks. The U.S. Navy continued to require the AAFAC to commit sizeable forces in these areas to counter what was a diminishing German threat the five to ten submarines that Admiral Doenitz kept along the U.S. coast and in the Caribbean Sea. From September 1942 until mid1944 these few submarines maintained pressure on the American anti submarine forces. To counter the submarine threat in the Caribbean, the Army Air Forces anti submarine Command continued to fly patrols and escort coverage from Cuba. These operations, which had begun as early as June 1942, generally kept the German submariners from making successful attacks in the Caribbean Sea Frontier, although two ships were sunk there as late as July 1943.

The Germans found the hunting more profitable in the area of Trinidad until midyear 1943. The AAFAC consequently based B-18's at Edinburgh Field, Trinidad, from early January until August 1943. In November and December 1942, German submarines sank 18 ships. Increased aerial patrols paid off with no losses of friendly ships near Trinidad from January to July 1943. During this time, the USAAF B-18's engaged mostly in convoy escort and coverage missions. In July-August, German submarines sank four merchant vessels. The USAAF anti submarine squadrons, flying both B-24's and B-18's, made six attacks and participated in two killer hunts to foil the enemy offensive in Trinidad waters.

In addition to the Trinidad area, the German submarines operated extensively in the South Atlantic Ocean in 1943, where merchant vessels sailed independently because there was no convoy system. The AAFAC sent a detachment of B-24 aircraft in May from Trinidad to Natal, Brazil, to patrol the South Atlantic sea lanes at ranges beyond the reach of the Brazilian Air Force. The next month, the detachment moved to Ascension Island, added two more aircraft, and flew patrols over the South Atlantic Ocean until August 1943.

Although important, the AAFAC's operations from October 1942 in the Eastern Sea Frontier, the Gulf Sea Frontier, and the Caribbean Sea Frontier constituted only a small part of the war against the German submarines. In fact, by midsummer 1942, the U.S. Navy's and the USAAF's anti submarine warfare efforts had forced Admiral Doenitz to withdraw most of his forces from these areas. The German submarines moved back to the North Atlantic to exploit weaknesses in Allied anti submarine efforts there. Consequently, the AAFAC turned to the reinforcement of the meager anti submarine air forces in Newfoundland.


OCTOBER 1941 - JULY 1943

In October 1941, far to the north, an USAAF detachment of four to six B-17's had begun anti submarine patrols over the northwest Atlantic Ocean from Gander Lake, Newfoundland. The B-17's were armed with machine guns and bombs but carried no radar or depth charges. In July 1942, the 421st Bombardment Squadron (Heavy), also flying B-17's and with a primary mission of long range bombardment training, replaced the detachment. The squadron cooperated with Royal Canadian Air Force and U.S. Navy organizations in Newfoundland to carry on its secondary mission of anti submarine war. Then, in the fall of 1942, the Army Air Forces anti submarine Command made anti submarine patrol the squadron's primary mission, re designating it the 20th anti submarine Squadron (Heavy).

The 421st had replaced the B-17 detachment in Newfoundland even as the Germans increased submarine activity in the 500mile (805 km) gap between 25 and 45 degrees West longitude that the Allies could not cover with land based aircraft. This gap in air coverage allowed the German submarine wolf packs to attack convoys without being spotted or attacked from the air. Admiral Doenitz organized the submarines in two screens running in a northwesterly direction at either end to catch the convoys as they sailed into the gap. The sea lanes northeast of Newfoundland, marking the eastern edge of Allied air coverage, were especially dangerous.

The Allied convoys sailed under several other disadvantages from September 1942 until March 1943. Fuel shortages kept them close to the shortest track to and from Great Britain. Winter weather favored the submarines which often approached the convoys without being detected until too late. For most of 1942 the British could not decipher Enigma transmitted code, but the Germans could read the Allied convoy code. The Germans located and intercepted Allied convoys more frequently and successfully during this period than at any other time in the war.

Germany redeployed its submarines to the mid Atlantic in June and July 1942, and the offensive became effective in July and August. By then, the enemy had 86 submarines in the North Atlantic, and approximately this number remained operational there until June 1943. In August and September 1942, the submarines located 21 of 65 convoys that sailed, attacked seven, and sank 43 Allied ships.

During the Allied Conference in January 1943 at Casablanca, French Morocco, Great Britain and the United States agreed to deploy B-24 aircraft to patrol the mid Atlantic gap. Modified B-24's, with a radius up to 1,000 miles (1,609 km), could fly day or night in all but the worst weather to detect and attack submarines. The British immediately began operating Liberators, the Royal Air Force designation of the B-24, from bases in Ireland and Iceland to cover the eastern part of the gap, but the U.S. Navy did not send any aircraft to cover the western stretches of the mid Atlantic. During February 1943 21 ships totaling almost 200,000 tons were lost, mostly in the western gap. The next month in the Atlantic, the Allies lost 38 ships of 750,000 tons and an escort in four convoys.

On 18 March a B-24 detachment of the 25th anti submarine Wing established a headquarters at St. John's, Newfoundland, and began anti submarine patrols on 3 April 1943. By the end of the month the Army Air Forces anti submarine Command had three B-24 squadrons operating from St. John's and Gander Lake, Newfoundland. The squadrons engaged in convoy coverage and in broad offensive sweeps ahead of the convoys. In April and May they made 12 sightings of German submarines, which resulted in three attacks, but the B-24's did not sink a submarine.

During April 1943, Allied long range B-24 aircraft and escort carriers closed the mid Atlantic gap in air coverage, effectively neutralizing the German submarine offensive. That month the Germans sank only three Allied merchant vessels while losing four submarines. In May Germany lost 31 submarines in the North Atlantic, and on 26 May, Admiral Doenitz withdrew his boats from the North Atlantic, essentially conceding victory to the Allies in the Battle of the Atlantic. Almost 1,700 Allied ships crossed the ocean in June and July 1943 without a loss.

The Battle against the U-boat
in the American Theater

   Part I
   Part II
   Part III

Allied air forces