Military history

EXPLOITING BRITISH ANTISUBMARINE TECHNOLOGY

The British continued to badger the Americans to organize convoys on the United States East Coast. Toward that end, Churchill and Pound offered Roosevelt and King, in addition to the ten corvettes, twenty-four British ASW trawlers, as well as ten motor torpedo boats under construction in Canada. King eagerly accepted the twenty-four trawlers but declined the Canadian vessels because the “Sixty Ships in Sixty Days” were to be completed long before the Canadian vessels, or so it was thought.

The British War Cabinet sent several military missions to the United States. Their purpose was to give the Americans the benefit of the British experience with U-boats and find out if the Americans were “really short of escort craft on the East Coast,” and if, as suspected, King was siphoning off the destroyers released from the North Atlantic run to reinforce the Pacific Fleet. Predictably, the reports of these missions were uniformly negative. The Americans had not yet learned how difficult it was to find and kill a U-boat. There was little to no coordination between the air and naval forces—no single operations center. In total numbers, the air and naval ASW forces were “quite inadequate.” There was as yet no single guiding hand within the U.S. Navy to formulate ASW tactical doctrine and to prescribe training methods and to coordinate R&D for new weaponry. The weaponry available was inadequate to the task. For example, American depth charges had a maximum depth setting of only 300 feet.

All this was undeniable. The reports later provided rich grist for those historians who sought to make the case that the Americans had “learned nothing” from the British experience with U-boats and/or that they—and King—had failed to grasp or were oblivious to the U-boat threat. But the reports failed to take notice of the very large number of ASW measures underway in America over and above the massive ship and aircraft building and repair programs. A great many of these ASW measures were a direct outgrowth of the British experience:

THE MOBILIZATION OF SCIENCE. Emulating the British example, in June 1940, America had mobilized its huge scientific and engineering community to assist the military. President Roosevelt had established the National Defense Research Committee, chaired by Dr. Vannevar Bush. Composed of a glittering array of eminent scientists, the committee had recruited thousands of willing scientists and engineers who had fanned out through the military establishments to contribute their talent to the war effort or who pursued military projects in their own institutions and laboratories.

The Navy bureaus and the Naval Research Laboratory (NRL) did not always welcome this outside talent with open arms. Many of the civilian scientists met calculated hostility. Nonetheless, by the time America entered the war the Vannevar Bush committee or its offshoots had launched a great array of ASW projects, based upon the work of British or American scientists, engineers, and mathematicians, some of whom had adopted the new British technique of “operations research.”

RADAR. Based on the British cavity magnetron, American R&D on radar had grown enormously. By January 1, 1942, MIT’s Radiation Laboratory had fifty different radar projects in the works. However, quantity production of centimetric-wavelength radar for naval ships and aircraft proved difficult. According to one authority,* “not a single microwave [centimetric] set was in use” on January 1, 1942. But the groundwork was well laid and the breakthroughs came quickly. On February 17, the Navy contracted for mass production of a 300-pound airborne (air to surface) centimetric-wavelength radar, Model AS-G (known colloquially as “George”), which could detect a coastline at a range of 100 miles, convoys at eighty-five miles, and surfaced U-boats at nine miles or more. Contracts for powerful long-range shipborne (surface to surface) centimetric-wavelength radar (Model S-G, also called “George”) followed almost immediately.

HUFF DUFF. Encouraged by the work of British and French radio engineers, as well as American specialists in that field, the NRL was pursuing with highest priority R&D on a High Frequency Direction Finder (Huff Duff) for ship-board installation. Spearheaded by the NRL’s Maxwell K. Goldstein, who worked in collaboration with engineers at International Telephone and Radio Laboratories, the R&D led to a set, designated Model DAQ. It, together with the British Model FH-3, was installed in the new destroyer Corry in the early months of 1942 for comparative tests.

The upshot was the development of yet another American set, DAR, which was put into “mass” production in the late summer of 1942. In Goldstein’s words, the DAR was an extensively modernized version of the British FH-3. While it utilized “most of the basic components” of the FH-3, the DAR incorporated “the complete use of U.S. tubes, stabilization of the radio frequency oscillator, a new ‘on course’ indicator of the cathode-ray type and a new power supply (with speaker) of compact design.”

The DAR (and its variations) was to become one of the most effective ASW “tools” of World War II. Parallel to its development, engineers at the NRL and at International Telephone and Radio Laboratories produced an equally effective land-based Huff Duff, Model DAJ.

DEPTH CHARGES. As the British reports noted, American depth charges had an unacceptable depth limit of 300 feet. American scientists discovered other faults. The charges sank too slowly and followed an erratic underwater trajectory. The warheads were too weak. A crash R&D program was already underway to produce depth charges with 600-foot depth limits, faster sinking rates, improved trajectories, and 50 percent more explosive power, by substituting the British-developed Torpex for TNT. Two reliable standard depth charges for surface vessels were soon to emerge: the Mark VII, with a 600-pound warhead, and the Mark IX, with a 300-pound warhead. The big Mark VII could only be rolled from the stern tracks. The smaller Mark IX could be rolled from stern tracks or fired from Y guns or the improved K guns.

EXPENDABLE SONOBUOYS. British scientists had proposed an ingenious device, the sonic- or sonobuoy, which was designed to be tossed from a merchant ship or escort during a suspected or actual U-boat attack. Fitted with a miniaturized hydrophone and a radio transmitter, the sonobuoy would float free to the rear of the convoy, where it could pick up the noise of a submerged submarine and send a warning signal.

The British did not pursue the sonobuoy, but the Americans, believing the device had great potential, had launched a large R&D program to produce improved sonobuoys for aircraft. Upon reaching the suspected area of a submarine or after detecting one by sight, the aircraft was to drop a pattern of sonobuoys. Since each buoy was to have a different coded signal, the aircraft would be able to follow the submerged moves of the submarine and set up an attack based on the detected movement, and/or call in surface forces to assist in the attack.

AIR-DROPPED WEAPONS. By the time the United States entered the war, the British, but not the Americans, had developed an aerial depth-charge pistol with a shallow setting of about twenty-five feet for attacking surfaced or crash diving U-boats. Profiting from British technology, the Americans hastened to fit a version of this pistol to the 250-pound Mark XVII aerial depth charge. Moreover, by substituting British-developed Torpex for TNT, the Americans increased the lethality of the aerial depth charge by 50 percent.

Aware from the British experience that aircraft attacks on U-boats had not been very successful, American scientists sought a more sophisticated device for killing fast-diving U-boats. The upshot was a small, smart, acoustic airborne torpedo that, after entering the water, “homed” on the noise of the submerged U-boat.

Declared feasible in December 1941, scientists and engineers at the Harvard Underwater Sound Laboratory, the Columbia University Underwater Sound Laboratory, the Navy’s David Taylor Model Basin, General Electric, and Western Electric and its subsidiary Bell Laboratories pursued this weapon with the highest priority in utmost secrecy using the cover name “Mark XXIV Mine.” Informally known as “Fido,” this weapon was ready for use in merely twelve months. It would prove to be one of the most effective ASW devices produced during the war, so successful that the original order for 10,000 torpedoes was cut back to 4,000.

The “Fido” was seven feet long and seventeen inches in diameter. It weighed 680 pounds and had a 92-pound Torpex warhead. It could “chase” a submerged U-boat for ten minutes at a maximum speed of 12 knots. Since a U-boat could outsmart Fido by surfacing and running away at high speed on diesels, the characteristics of Fido remained very secret throughout the war, to the point that the weapon could not be employed except on a fully submerged U-boat, and not even then if an Allied ship or another U-boat was on the surface nearby.

LORAN. The British experience had demonstrated that a means of all-weather navigation was essential for reporting positions of sighted U-boats, for more effective rendezvous of convoys with air and surface escorts, for evasive maneuvers of convoys, and for other military purposes.

In October 1940, an American scientist, Alfred Loomis, proposed an electronic navigation system which was based on radio pulses emitted in a certain way by shore-based transmitters. In early 1941 a team at MIT’s Radiation Laboratory, headed by Melville Eastham, pursued this proposal and by September of that year had demonstrated its feasibility. Known as Long Range Aid to Navigation (LORAN), the system proved to be capable of providing nearly precise navigational fixes up to 700 miles from the shore-based transmitters in daytime and 1,400 miles at night in any weather. Soon after America entered the war, the Army and Navy established five LORAN transmitting stations in Canada and Greenland, for the benefit of the North Atlantic convoy network. From this beginning, the LORAN system was to spread over half the globe.

MAGNETIC AIRBORNE DETECTOR (MAD). American scientists had suggested before the war that the mass of metal of a submerged submarine could probably be detected from a low-flying aircraft equipped with a magnetometer. In October 1941, a Catalina equipped with primitive MAD gear verified the theory and by the time America entered the war, a very large MAD R&D program was underway to intensify the sensitivity of the magnetometer. An improved MAD had been installed in a blimp based on the East Coast and sets were being installed in other blimps.

Upon getting a MAD contact, the blimp dropped floating flares or lights to mark the course of the submerged submarine so that it or other ASW forces could set up an attack. To make the flares and lights fall vertically—and accurately—they were fired backward at a speed equal to the forward motion of the blimp. R&D was underway to reduce the weight of MAD gear so that units could be mounted on each wingtip of fixed-wing aircraft, to provide improved “directionality,” and for a Magnetic Airborne Bomb Sight (MABS). The latter was to compensate for the forward speed of the aircraft and automatically fire bombs or rockets rearward which, like the flares and lights, were to fall vertically to the target.

SONAR AND SONAR PRESENTATION. Apart from work underway to greatly increase the power and sophistication of sonar, American scientists had urged development of an electronic “plotter,” which would simplify the difficult job of tracking and attacking submarines for the benefit of the unskilled reserves who were to man most of the Navy’s ships. The answer from the laboratories was the important Antisubmarine Course Plotter. Based on electronic inputs from the sonar and from the gyro compass and the pit log of the surface vessel, it automatically displayed on a cathode-ray tube the track of the submarine and the track of the attacking surface ship.

These and many other new devices were in due course to immeasurably assist the Allies in the U-boat war, but, as the British reports noted, there remained the absence of a single guiding hand to direct the Navy’s ASW effort. An important step to remedy this deficiency was taken on February 7, 1942—as the first wave of Drumbeat U-boats was arriving back in France. On that date Atlantic Fleet commander Royal Ingersoll established in Boston what was called the Atlantic Fleet ASW Unit, commanded by Wilder D. Baker, an experienced destroyerman and escort-group commander, detached from the North Atlantic convoy run.

The purpose of the Baker group was to develop and standardize tactics, weaponry, and training for killing U-boats. At King’s direction or invitation, all Sea Frontiers and the Army Air Forces attached liaison officers to the unit. At Baker’s invitation, ten men skilled in “operations research” from a division of the National Defense Research Committee, known as the Antisubmarine Warfare Operations Research Group (ASWORG), joined his unit. Soon after the unit was staffed, King transferred it from Boston to his headquarters in Washington, and bestowed upon it extraordinary powers.

Emulating the British example in its earliest days, the Baker group produced manuals for carrying out attacks on U-boats and also for “attack teachers.” The latter were elaborate hands-on layouts to simulate battles versus U-boats. Evolved from “a few” imported British models, the American attack teachers were produced by three firms: General Electric, Sangamo, and the Submarine Signal Company. As in the Royal Navy, the U.S. Navy required that all American officers involved with ASW had to master the intricacies of the attack teacher.

At the Federal Building in downtown Manhattan, meanwhile, Admiral Andrews and General Krogstad had to improvise with the inadequate “tools” at hand. The “tatterdemalion fleet” of the Eastern Sea Frontier, augmented by a few Navy minesweepers, tugboats, and other utility craft—whatever could get to sea—patrolled close offshore, but these little ships were so busy searching for and picking up survivors of the many torpedoed ships that they had little time for hunting and fighting U-boats. The Navy and Coast Guard aircraft and blimps patrolled the inner shipping lanes. Krogstad’s keen but green bomber pilots, alternating basic bomber training with ASW patrols, reconnoitered lanes further offshore. Several air crews found and attacked what they believed to be U-boats, but these contacts were doubtless products of overactive imaginations.

The British continued to pressure King to initiate convoying on the United States East Coast. However, King, Ingersoll, Andrews, and all other senior naval officers resisted this pressure because they did not believe, as the British did, that inadequately escorted cargo convoys were better than no convoys at all. The American view had been formed to a great extent by the severe British shipping losses in the thinly escorted North Atlantic convoys of the summer and fall of 1940 and on the losses in the fall of 1941 on the North Atlantic run when inadequately trained and equipped Canadian vessels served as convoy escort. The abort of the Canadian-escorted Slow Convoy 52 in Newfoundland waters in early November 1941 was still vivid in American minds and doubtless influenced King and others.

In his attack on the U.S. Navy, historian Michael Gannon argues that inasmuch as Dönitz had focused his U-boats on “America’s doorstep,” leaving the North Atlantic convoy run “quiet,” the Allies should have immediately shifted the bulk of ASW and escort forces from North Atlantic to North American waters, both to attack U-boats and to provide escorts for an East Coast convoy network.

This argument, which appears logical and prudent, is, in fact, neither.

• The North Atlantic convoy run was definitely not “quiet,” meaning un-threatened. The U-boats, en route to and from the Americas, crossed the North Atlantic along routes approximately the same as the convoys. Since the U-boats traveled alone, rather than in groups, or wolf packs, and maintained radio silence, they were very difficult to locate and evade. Any one of those U-boats could happen upon a North Atlantic convoy at any hour. If the convoy was not properly escorted, the result could be catastrophic.*

• In the initial wave of U-boats Dönitz sent to the Americas, twelve of the fifteen boats went to Canadian waters. They patrolled off Halifax, St. John’s, and Sydney, where transatlantic convoys originated and dispersed. Deprived of proper escorts, these convoys could be massacred in Canadian waters by succeeding waves of U-boats.

• Owing to Hitler’s “Norway paranoia,” in early January Berlin ordered Dönitz to establish a defensive line of U-boats between Iceland and the Faeroes. Although some of these boats assumed positions to the north of the regular convoy routes in the Northwest Approaches, as will be seen, they posed a definite threat to inbound North Atlantic convoys as they entered and departed the British Isles. To leave those convoys unescorted could also invite catastrophe.

• The U.S. Navy was already in the process of shifting its patrol bombers and many of its destroyers from the North Atlantic run to American waters, as noted, leaving the preponderance of the escort job on the North Atlantic run to the Canadians and British. As also noted, most of these American destroyers had to be assigned to escort troopship convoys. To uproot the remaining Canadian and British escorts and also move them to East Coast waters not only would have exposed the North Atlantic convoy run to U-boat attack, but also would have placed those warships far from home bases and supply lines, decreasing their effectiveness and availability.

Meanwhile, Admiral Andrews continued to provide Allied shipping all the protection he could with “the tools at hand.” He laid defensive minefields on the approaches to the main Atlantic ports: Portland, Maine; Boston; New York; Charleston; and the entrances to the Delaware and Chesapeake bays off Cape May, New Jersey, and Cape Henry, Virginia. He pulled back shipping from well offshore to newly marked inshore lanes very close to the beach in shallow water, where U-boats were less likely to be and where the few available aircraft might offer a modicum of protection. He encouraged the use of protected shortcuts, such as the Cape Cod Canal. He advised merchant ships to exercise strict smoke discipline, to lay over in port at night if possible, or to run blacked out and to zigzag and to minimize radio transmissions, which U-boats might monitor. Unaccustomed to all this rigamarole—or contemptuous of being told what to do by the Navy—the captains of many American merchant ships simply ignored the rules and did what they pleased, and not a few lost their ships.

As a result of the sinkings in the Eastern Sea Frontier, on January 24 King directed Ingersoll to make available to Andrews and to other Sea Frontier commanders Atlantic Fleet aircraft which were based within their respective areas of responsibility. This gave Andrews operational control of forty-four Catalinas, thirty-eight at Norfolk and six at Newport. Ingersoll notified “all Sea Frontier commanders” that the transfers were not permanent but rather a temporary “emergency measure.” He stressed that the use of such planes for ASW patrols by Sea Frontiers “should not unduly interfere with scheduled operations of Atlantic Fleet aircraft, especially those on convoy escort.”*

Shocked and bewildered by the Japanese successes in the Pacific and Far East, the American public was at first only dimly aware of the gravity of the U-boat campaign in American waters. The Navy did its utmost to keep Americans in the dark by imposing censorship, by downplaying—or lying about—the extent of shipping losses, and by issuing reassuring claims of U-boat kills. A member of the Washington naval staff, Ladislas Farago, asserted in his book The Tenth Fleet that a Navy publicist even deliberately fabricated the legendary radio message from one Argentia-based Hudson pilot, Donald F. Mason, who erroneously claimed a kill: “Sighted Sub. Sank Same.” But, in fact, as Admiral Bristol in Argentia asserted in an after-action report to Ingersoll on January 28 (copies to King and Stark), the cry of triumph from Mason was quite genuine, even though he had not actually sunk a U-boat.*

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