The lull in submarine activity in the Atlantic during the first half of 1916 had been prompted largely by American diplomatic protests. Germany’s failure to bring about a favorable resolution to the war at Verdun and the heavy fighting at the Somme brought home the prospects of eventual defeat. Balanced against the possibility of losing the war the political risk of offending the United States seemed one worth taking. U-boats resumed hunting prey in British home waters in August 1916 and the new threat prompted the British to expand seaplane patrols in September. In response, Adm. Stanley Cecil Colville, commander of the Royal Navy at Portsmouth, requested installation of a four-machine seaplane base at Portland to supplement the existing facility at Calshot and two more SS stations, one for the Isle of Wight and one for Portland, each with ten airships.
Actions like Colville’s proved preliminary to a wholesale reorganization of the war against the U-boat and, on December 18, 1916, the Admiralty created the Anti-Submarine Division (ASD). The new organization took a special interest in aviation and vastly expanded both the number of heavier- and lighter-than-air craft available and the role of its aerial assets in the anti-submarine campaign. Creation of the Anti-Submarine Division centralized naval aerial activities that previously had been left to the individual prerogatives of each region’s senior naval officer. The new division organized a coordinated system of coastal patrols and split naval aviation according to its offensive and defensive functions, much as the Dover Command had earlier divided its organization into reconnaissance, bombing, and fighting wings. Offensive assets included the airplanes and seaplanes patrolling Britain’s waters actively hunting submarines, purely defensive reconnaissance missions being left to airships due to their endurance. Given these measures made areas near the coasts safer but left ships farther out to sea to their own devices, the director of the ASD further recommended enhancing direct protection of the fleet by equipping British vessels with kite balloons to improve their fields of vision.
By January 1917 the British had built a massive naval aviation program that combined three seaplane carriers in service with more under construction, ships equipped with kite balloons, plans for rigid airships, coastal airships protecting the home waters, and large seaplanes able to patrol farther away. Yet, despite this abundance of assets, Adm. Sir David Beatty, commander-in-chief of the Grand Fleet, regarded his air strength insufficient compared with his needs and recommended to the Admiralty that: “all naval officers who are engaged upon duties not connected with the fleet should be withdrawn and utilized for developing the Royal Naval Air Service.”
The early months of 1917 also saw Germany remove all remaining restraints from its U-boat commanders, resuming unrestricted submarine warfare that the German High Command hoped would bring the war to a successful conclusion within six months. Instead, within just over two months the decision to escalate its cruiser war produced the outcome Germany most hoped to avoid. On April 6, 1917, the United States declared war on Germany. Ultimately, the resumption of unrestricted attacks combined with a botched German attempt to recruit Mexico into the war on its side, prompted the United States to enter the conflict.
The U-boat war reached its peak coincident with the American entry into the war. The last half of April 1917 saw approximately 50 percent of the German submarine fleet at sea with five ships sunk on average each day. The 19th proved the worst single day of the month for the Allied merchant fleet, when U-boats and German mines sunk eleven ships and eight fishing vessels. This spike in submarine activity pushed the average for the year 1917 to three ships sunk per day. As part of the British response the RNAS laid out formal areas for aerial patrols and categorized those missions as “routine,” “emergency,” and “contact,” with contact flights reserved for its seaplanes. Beginning operations in late April, the new patrol system received formal Admiralty sanction on May 8, 1917. Station commanders at Nore, Harwich, Yarmouth, Killingholme, South Shields, Dundee, and Houton Bay coordinated patrol hours and areas in systematic fashion to avoid overlap and to ensure that each district had at least one aircraft on duty in the air during all possible flight hours.
The British further refined their naval aerial reconnaissance system in the spring of 1917 designing both the spider web system and Tracing U. The spider web created an imaginary octagon of chords radiating 60 miles out of the North Hinder light ship in the English Channel, an epicenter around which seaplanes could systematically patrol guaranteeing maximum coverage with a minimum supply of aircraft. Spider web patrols began on April 13, 1917, and in the first eighteen days five flying boats flew twenty-seven patrols sighting eight U-boats and bombing three. Tracing U (“U” for U-boat) divided the southern portion of the North Sea into grids similar to those in common use by artillery units operating on the Western Front, allowing commanders of coastal air stations to quickly pinpoint submarine sightings, then dispatch attacking aircraft or communicate the information to nearby destroyers.
Organizational refinements to the reconnaissance and patrol system proved effective and valuable, but the adoption of the convoy system in late April 1917 proved the most significant move forward toward defeating the submarine. To this point in the war many senior commanders in the British Admiralty opposed convoying merchant vessels believing that warships should be reserved for offensive action rather than escort duty. The large increase in sinkings that followed Germany’s resumption of unrestricted submarine warfare in February, the success of an experiment in protecting French coal vessels begun the same month, and the entry of the United States into the war in April combined to reverse their opinions. Furthermore, America’s enlistment in the Allied cause increased the number of ships available for convoy duty and opened US ports for use as convoy assembly points.
The added naval capacity brought with it greater responsibility for Allied aviators. In order to protect the Atlantic courses over which the American Expeditionary Force and its equipment would travel naval aviation expanded its former role in protecting Anglo-French military traffic and neutral merchant shipping during the last half of 1917. Land-based airplanes and seaplanes could patrol the areas off the British and French coasts to the extent of their range covering the arrival of ships during the last leg of their travel from the United States. Kite balloons towed by warships could extend the effective field of vision of the convoy before the aerial escort picked it up, allowing crews a lifesaving early look at potential attackers throughout the journey. The British strengthened the new system further by completing construction of the network of airship stations the RNAS had begun organizing in 1916, the last becoming fully operational by the end of 1917. The RNAS, of course, protected the British coast and that portion of the French shoreline most vital to arriving British traffic. The French Navy also vigorously defended its own ports, but paid more attention to the Mediterranean and the Adriatic, leaving the Atlantic largely to their British allies and later to the AEF. The US Navy joined the effort within a few months of the American declaration of war and throughout 1918 expanded the network of protective air stations further still, taking over some British, French, and Italian coastal bases and constructing some of its own.
After the task of organizing an American army, an army that barely existed when the United States declared war, protection of that force as it crossed the Atlantic to fight on the Western Front represented the most important job facing American military and naval leaders in April 1917. In addition to the naval air stations they would build or take over in Europe, US Navy commanders faced the challenge of defending embarkation and receiving bases on their own side of the Atlantic, as well as a small number of less vulnerable installations on the Pacific coast. Even with aerial patrols fully operational the Navy would have to defend its ships against German submarines through most of the Atlantic crossing without the direct assistance of airplanes owing to the limited range of aircraft operating out of its coastal air stations. Taking their cue from British and French experience, American naval commanders enhanced the safety of the US fleet during that vulnerable period by equipping nearly every class of its ships with balloons to provide cover for the convoys.
Building the aerial organization necessary to protect the fleet required putting US naval aviators on duty in France as quickly as possible. Within five weeks of the American declaration of war the Navy dispatched Lt. Kenneth Whiting to take charge of the first group of naval flight trainees sent to France. Training preparations progressed well enough that by July the Navy reported to the French that two schools had been established within the French interior, one at Tours to instruct pilots and the second at San Raphael for prospective mechanics and observers. Plans had also been made for an additional school to teach naval artillery observation as well as an operational station at Moutchic-Lacanau.
Once trained the Navy’s aviators would serve at a network of stations in the planning stages or already under construction on both sides of the Atlantic. By July 1917 provisional plans existed for the organization of naval air stations at Dunkerque, Le Croisic, and St. Trojan in addition to the facilities at Tours, San Raphael and Moutchic-Lacanau. Operations commenced at Moutchic-Lacanau on November 11, 1917 and within a week the naval air station at Le Croisic launched the first of an eventual 1,045 wartime patrol flights.
By the following April another four stations had opened in Great Britain and France, at Killingholme, Ile Tudy, Dunkerque, and Paimboeuf, as well as a base at Bolsena, Italy. Patrols from these and the extant British and French air bases impressively demonstrated the value of aerial reconnaissance to the convoy system. In the spring, RAdm. Henry G. Wilson told the French press that cooperation between the French and US navies had substantially reduced sinkings in the waters along the French coast, comparing October 1917, during which thirty-four ships were torpedoed to February and April 1918, when no ships had been lost to the U-boats.
Though submarine losses directly attributable to aircraft action are difficult to document, the mere presence of airplanes or airships frequently played critical roles in the demise of U-boats. Two incidents, both of which coincidentally took place on April 24, 1918, provide typical examples. In the first, airship SSZ 41, stationed at RAF Polegate received a report of a submarine operating southeast of the Isle of Wight. In response, the crew patrolled in the vicinity of the submarine’s reported sighting for twelve hours in a dense fog, returning without having sighted the U-boat. A torpedo boat destroyer found and sank the German raider later in the morning. Official speculation held that the submarine had been forced to remain submerged in order to avoid detection by the airship and that by morning the desperate need for fresh air and recharged batteries forced the boat to the surface, putting it in a situation where it could no longer avoid detection.
The second incident further demonstrates the potential of air-sea cooperation. Two American seaplanes patrolling off the French coast near Penmarch spotted what they believed to be a German submarine operating two miles from a convoy, responding to the opportunity with two bombs. Tracking the encounter, USS Stewart left its position in the convoy to investigate. While en route, the Stewart watched the aircraft mark the site with smoke bombs and, on arriving at the scene the American ship dropped depth charges after which the crew observed oil on the surface. Though no wreckage surfaced, other ships in the vicinity observed oil as late as two days later, providing strong evidence of a sinking.
The success of the patrols and the convoy system firmly established what the world’s navies had been learning throughout the war—that extending the vision of ships using aerial observers saved lives and material. Over the course of the war’s remaining months the US Navy established a dozen stateside naval air bases, in addition to a pair in Canada, one each in the Azores and the Panama Canal Zone, and a total of twenty-seven air stations in Europe. The stations on the American side of the Atlantic functioned primarily as coastal patrol stations protecting the convoy assembly points from the threat of German submarines. The nineteen naval air stations on the European side of the Atlantic that conducted similar reconnaissance flights generally communicated their sightings to nearby ships but occasionally launched their own attacks on real or suspected submarines.
Considering naval heavier- and lighter-than-air units along with the Army’s airplanes and balloon sections makes it clear that American aviation had reconnaissance and observation as its main purpose. Fifteen North American naval air stations and one in the Panama Canal Zone had reconnaissance as their primary duty, as did nineteen of the US Navy’s twenty-seven European stations. In comparison, the French established a total of thirty-six coastal seaplane bases, as well as a half dozen balloon centers, and four dirigible bases. Adding those thirty-five American bases to the forty-five US Air Service airplane squadrons and the seventeen American balloon companies working on the Western Front raises the total number of American aviation units that served during the conflict to ninety-seven, out of which seventy, or 72 percent, performed reconnaissance or observation as their primary function. Regardless of how military and naval air power developed over the rest of the twentieth century, during the First World War its principal and most valuable function lay in the aviators’ ability to see and report what happened on the ground and water.
The numbers of aircraft acquired by the world’s navies during the war further document the growing appreciation for aviation. The British Navy increased its heavier-than-air aircraft stock from fewer than one hundred to nearly three thousand, its airship strength from six to 111, and its inventory of captive balloons from two to 200. The Deutsch Kriegsmarine air fleet grew from twenty-four air- and seaplanes to nearly 1,500, and its lighter-than-air division worked its way through eighty-three airships, beginning the war with one and making it to the armistice with nineteen. The French Navy enlarged its heavier-than-air aircraft supplies from eight at the outset of war to 1,264 at the end, alongside fifty-eight airships and 198 kite balloons. Even the more limited resources of Austria-Hungary and Italy grew exponentially, the Austro-Hungarian air- and seaplane fleet expanding between eleven- and twelve-fold and the Italian inventory by more than twenty-fold. For its part, over the relatively short time it spent at war the US Navy grew its aircraft inventory from fifty-four airplanes and seaplanes, one airship, and two balloons in April 1917 to over 2,100 heavier-than-aircraft, fifteen airships, and more than two hundred balloons at the armistice.64 These figures reflect the same kind of progress the world’s other warring powers made during the conflict.
Although these dramatic operational changes and numerical increases speak to how thoroughly aviation had been accepted into the world’s navies, they do not begin to hint at the change in character the presence of aircraft brought to the war at sea. Although aircraft may have failed to live up to naval leaders’ prewar expectations due to airframe and powerplant technological limitations, through its reconnaissance function naval aviation prevented many potential sea disasters. History’s failure to acknowledge this enormous contribution lies in the challenge proving a negative always presents to the post-event analyst. In evaluating the impact of the RNAS/RFC merger that created the Royal Air Force on April 1, 1918, one historian argued the demise of the Royal Naval Air Service “crippled Britain’s credibility as a sea power.” During the First World War and afterwards the US Navy arrived at the same conclusion. The day had arrived when a modern navy seeking to project its nation’s power around the globe could not hope to compete without its aircraft.