The Listeners is a significant, long overdue study of First World War anti-submarine warfare, in particular, the crucial American development and application of hydrophone technology after the US entry into the war (6 Apr. 1917) and its contribution to the ultimate victory over Germany's U-boats in 1918. While the outlines of the anti-submarine campaign are familiar from popular histories that highlight dramatic Q-ship engagements or the sinking of the Lusitania, the same cannot be said about the technical details of the critical anti-submarine work done by scientists in Britain and America. In this timely centenary assessment of the First World War at sea, Roy Manstan (Univ. of Birmingham) follows in the footsteps of historians like Willem Hackman[1] and Dwight Messimer.[2] The book also nicely complements specialized studies of the Royal Navy's Air Service[3] and anti-submarine campaign at specific district commands at Dover and in Ireland.[4]

The strength of The Listeners is its focus on the technical and tactical advances of the US Navy (USN) that led to the Allied victory over German submarines. Manstan's background as a USN acoustical engineer and Master of Science degree-holder (Univ. of Connecticut) gives him a useful perspective on subjects ranging from Scuba-diving and maritime zoology to David Bushnell's famous 1775 Turtle submersible. His lively and clear prose style makes for compelling reading, despite the sometimes esoteric nature of his subject matter.

Manstan begins by sketching the historical background of the submarine war, from the sinking of the armored cruisers Cressy, Hogue, and Aboukir in September 1914 to the Royal Navy's early research efforts to counter Germany's U-boats. He then turns to his principal interest: the development of America's early hydrophones. He stresses how quickly US and Allied anti-submarine detection efforts evolved over a few short years of war; he highlights the technological contribution of the United States to the war effort, something not generally recognized in the literature.

The author concentrates on the formation and work of the Naval Consulting Board station at Nahant, Mass. (105) and the National Research Council's station at New London, Conn. (111). Both institutions fell under the authority of the Special Board on Antisubmarine Devices established by Secretary of the Navy Josephus Daniels in summer 1917 to oversee all American anti-submarine developments. With input from inventive geniuses like Thomas Edison, serious efforts to create practical American hydrophones were soon underway.

Indeed, Manstan demonstrates, within a few months, sophisticated hydrophone systems and deployment platforms were rolling off the assembly lines. The USN planned to use the hydrophonic detection equipment alongside specially designed surface vessels and aircraft to triangulate the positions of enemy submarines along critical Atlantic coastal approaches, where gaps in the convoy system exposed Allied merchant ships and communications to U-boat interception. Manstan is in his element here: he provides superb technical descriptions and synthesizes otherwise opaque technical details with tactical applications.

These examples show the value of the prototype Broca instrument—one of dozens of systems devised and implemented by the Americans—but also reveal the complexity of binaural listening techniques, an important training and tactical consideration seldom treated in general histories of anti-submarine warfare. The discussion here is clarified by many careful primary source descriptions and the inclusion of many photographs and diagrams. Indeed, Manstan is at his best when synthesizing the scientific and technical aspects of the committee and experimental work that yielded tactical applications ranging from underwater sensors to radio communications and hydrophones.

The author is less compelling and painstaking in his handling the anti-submarine war itself, which he sandwiches between chapters on the development and implementation of hydrophones aboard USN submarine chasers. He is prone here to informality, unhelpful digressions, including one on mermaids (31), and minor errors such as mistaking First Lord of the Admiralty Arthur Balfour for First Sea Lord Sir Henry Jackson (92).

While the research in the primary scientific and operational chapters is soundly based on museum and family archives, the narrative chapters resort to the well-worn memoirs of, for example, Adm. William Sims and First Sea Lord John Jellicoe. Manstan also at times exaggerates the submarine threat for dramatic effect, downplaying the convoy escort system and aerial patrols that ensured the successful transport of vital war supplies (241). He correctly maintains that shipping loss rates remained significant for much of the war after July 1917, but by then the possibility of Allied defeat had been averted, for hydrophone-equipped submarine chasers and trained crew members had added another layer of security to the material-intensive Jellicoe-Sims approach to anti-submarine warfare.

The British side of the hydrophone story is briefly discussed, specifically the efforts of Cdr. C.P. Ryan to emplace hydrophone stations and "drifters" (21); Lord Fisher's Board of Invention and Research is treated in passing (25). The British side of affairs is, in general, not Manstan's focus; readers wishing more detail on Royal Navy efforts should consult the work of Elizabeth Bruton,[5] Curator of Engineering and Technology at the Science Museum, London.

Manstan does make clear just what a risk Germany took in disregarding America's entry into the war, not only in the well understood military terms, but in technical and scientific terms as well. In a matter of months, the United States was producing advanced hydrophones for platforms ranging from airships to surface vessels and even submarines.

The book also describes the role of USN Submarine Chasers (SCs), small, fast patrol craft designed to shield the coastal approaches to the English Channel outside areas protected by larger destroyers, much like the famous corvettes known from the Battle of the Atlantic in the Second World War. Equipped with American-made hydrophones, SCs patrolled in groups to locate and depth-charge German coastal submarines. Combined with aircraft and destroyer support, SC groups represented a potent anti-submarine weapon indeed.

Although specialist readers might wish for greater detail, Manstan's lucid prose and knack for explaining the technical details and scientific history behind it will raise the profile of anti-submarine technology with a broad general readership.