The Listeners. Roy R. Manstan
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What Germany hoped would end the war was the U-boat. The ground war had slogged into a lethal stalemate along the Western Front, and it had become apparent that a decisive battle—by either side—would not be possible. German scientists and engineers had developed an efficient predator in their U-boat, which had evolved from a small vessel designed for coastal defense to large cruisers capable of lengthy missions far from Germany, including the east coast of the United States. Twentieth-century technology created this new form of naval warfare; it would take twentieth-century technology to provide effective tools for the U-boat hunters. Some of those tools came from a unique organization established at the behest of President Woodrow Wilson—the Naval Experimental Station in New London, Connecticut. Formed soon after America joined the war, the station was staffed by civilian scientists and engineers supported by naval personnel—their mission: solve “the submarine problem.”
TO CATCH A GHOST
Allied warfare upon the submarine was still largely a game of blind man’s buff … We were constantly attempting to destroy an enemy we could not see. So far as this offensive at sea was concerned, the Allies found themselves in the position of a man who has suddenly gone blind … Deprived of sight, he is forced to form his contacts with the external world by using his other senses, especially those of touch and hearing.4
Once submerged, as Admiral William S. Sims understood, the elusive submarine became invisible. Offensive action against Germany’s fleet of submarines had depended on observations from ships and aircraft attempting to intercept a U-boat which had surfaced while on patrol. On rare occasions, an observer might see the wake of a U-boat periscope, or the track of a torpedo launched against some unwary vessel. The chase was on. A destroyer would track back along the path of the torpedo or to the last location given by an observer, hoping to ram the submarine before it was able to submerge to a depth below the destroyer, an approach proposed by Admiral George W. Melville, USN, as early as 1902:
There are … experts who believe that fast running boats will be able to run the submarine down … [Thus] with the submarine—being slow in action, and deficient in maneuvering qualities, the picket boat would have an opportunity to run over them before the submarine could disappear …”5
Destroyers also dropped depth charges, yet without knowing its target’s precise location, the submarine could easily maneuver beyond the area and avoid the force of the explosions. While troublesome, a random depth charge attack may have had little effect on a U-boat’s operation. The perceived invisibility of the U-boat, and the initial lack of an effective deterrent, led to an increased reliance by Germany on undersea warfare.
At the beginning of the war, Germany had twenty-eight submarines. Between August 1914 and November 1918, an additional 346 were produced. When Germany declared the waters around the British Isles a war zone in February, 1915, only thirty-seven submarines were available. As construction continued, and with losses sustained during the 1915 offensive, Germany’s submarine fleet had increased to sixty-four by December. Monthly commissioning rates increased in 1916, and on February 1, 1917, when Germany instituted her policy of unrestricted submarine warfare leading to America’s entry into the war, the fleet had increased to 152. At no time did the German submarine fleet exceed 180.6 While some of the large cruiser-sized submarines carried a compliment of around sixty, most U-boat crews numbered forty or less.7 By the end of the war, a total of 178 submarines were lost due to mines, depth charges, allied submarine torpedoes, and a variety of combat-related causes, including that brute force method of ramming a U-boat, which couldn’t escape the bow of a destroyer.8
Early in the war, it became evident that sounds produced by a submarine when submerged and underway could betray its location. For two years the British had attempted to exploit this vulnerability, but the expertise and tools available were rudimentary and the results were less effective than hoped for. Immediately after America entered the war, the scientists in New London and the Navy’s other experimental facilities worked in concert with their European counterparts to perfect a technology with which U-boat hunters could detect these sounds—then pursue, locate, and destroy the predator.
Much of the Navy’s antisubmarine development work occurred on, above, and under Long Island Sound, just beyond the harbor at New London. Under the guidance of the newly created Special Board on Antisubmarine Devices, with headquarters at the nearby submarine base, many of the technologies created by civilian scientists and their naval colleagues were soon on their way to the war. Well-trained “listeners” were anxious to hear their adversary attempting to slip away undetected. By 1918, now able to locate a U-boat with some precision, it became difficult for the submarine to evade an attack by a barrage of depth charges. If the U-boat avoided damage, crew morale did not. Without the listeners and their hydrophones, The War to End All Wars may have ended badly for the Allies.
A VOICE FROM 1918
“Periscope showing again on the sta’board bow!” the crow’s-nest lookout was roaring. Yes, there she goes—conning tower awash, and a feather of foam streaking behind her periscope as she races toward the north. It must be a mine-laying sub, surprised while laying her eggs off the entrance to Corfu … Just then she dives.9
In his memoir, The Splinter Fleet of the Otranto Barrage (1936), Ray Millholland described this encounter between a U-boat and a hunting group of American subchasers stationed at the Greek island of Corfu. As chief engineer on board SC-124, Millholland was on barrage duty along the passage between the Adriatic and Mediterranean, known as the Straits of Otranto. There was an abundance of secrecy associated with the subchasers and their activities, and Millholland carried those concerns into his memoir, only referring to his vessel as “1X4.” He used a fictitious name for his commanding officer, referring to him as the “skipper, Dorgan … a bull-necked, red-headed Irishman.” The actual commanding officer of SC-124 was a redheaded Irishman, Lieutenant Junior Grade (LTJG) “Red” Kelly, although history doesn’t confirm the size of his neck. Millholland’s story continues:
The big red hunting flag breaks out from our yardarm, signaling chasers A and C that we have sighted a submarine. Then the Stand By signal bangs out its warning on the alarm gong. Dorgan is getting set for a depth-bomb attack.
The engine-room deck plates bounce under our feet, and old 1X4 shudders in every frame. Dorgan has just kicked over his first depth bomb. Three more follow in rapid succession. Then comes the signal to stop all engines for a listening period.
Early in 1918, the first subchasers designed and equipped specifically for hunting Germany’s relentless underwater predators left New London, Connecticut, heading for the war zone. Over the next nine months, over one hundred of these fast, maneuverable 110-foot-long wooden-hulled vessels hunted day and night in the waters around Britain, France, and throughout the Mediterranean. The subchasers carried a new technology on board, which, when lowered beneath the surface, enabled well-trained sailors to hear the distinct sounds of a U-boat.
During the “listening period” Millholland referred to, an inverted T-shaped device known as an “SC-tube” was lowered from a housing near the keel. A sound sensor was mounted at each end of the horizontal section of pipe forming the “T,” with the vertical portion of the “T” passing through a watertight seal in the hull. Within the pipe, copper tubes connected each sound sensor to one of the listener’s ears through a stethoscope. As he rotated the “T,” the sound in each ear would be of the same intensity when the source of the sound—a U-boat—was perpendicular to the “T,” a process referred to as “binaural listening.” The same effect occurs when a person rotates his head to determine the direction of a sound in air. The SC-tube, however, could not be used when the vessel was underway; hence the vessel had to stop during the listening period.
Three subchasers, operating a distance apart but abreast, comprised a hunting group, where the central, or flagship, subchaser directed the pursuit: SC-124, in this case. All three had to stop for each listening period to obtain a bearing to the target. The flagship, which was in contact with the port and starboard wing chasers, plotted the three bearings; where they crossed was the approximate location of the sub at that time. Then from the captain of SC-124:
“Up