Learn from Fleet Boat Development

At the end of World War I, the U.S. Navy discovered that surrendered German U-boats were superior to U.S. submarines. The U-boats could go faster and farther, and they could carry almost twice as many weapons as the newest U.S. submarines. They also could submerge four times faster. The U.S. Navy’s subs possessed advantages only in maximum depth and an extra half knot submerged.¹ 

At the start of World War II 23 years later, however, the U.S. submarine force possessed versatile “fleet submarines” that proved their technological quality throughout the war.

The interwar development of the fleet submarine remains relevant. Today’s Navy has undertaken an aggressive program to develop new platforms and payloads, even as the United States’ competitive advantage shrinks or even disappears in some areas.² The architects of tomorrow’s fleet should study the lessons offered by their interwar ancestors and base design requirements off realistic strategy, refine requirements and technologies through operational feedback loops, take advantage of industrial collaboration, and accept contributions from the deckplates.

Strategic Vision and the Operational Feedback Loop

Even before World War I, the U.S. Navy evaluated the possibility of a future war involving Great Britain (code-named “Red”), Japan (code-named “Orange”), or both. The Red and Orange war plans established the idea for strategic employment of the submarine force. A short-range coastal-defense submarine would be sufficient to meet the demands of the Red plan, but War Plan Orange called for a more capable and longer-range submarine that could cross the Pacific, scout out the Japanese Navy, and soften it before the U.S. surface fleet closed to finish it off.³

Because the bigger, more capable submarine could carry out the lesser submarine’s missions, the Navy began developing “fleet submarines”—the V-boats—before the Great War even ended.⁴

Starting in the 1920s and until the brink of World War II, the Navy experimented. Although some of its experiments entailed only one submarine and one surface ship, other larger exercises—the famous Fleet Problems—assembled most, if not all, of the Navy. The service carried these out annually in the Caribbean, the Hawaiian Islands, or off the Panama Canal, practicing war plans and testing new technological capabilities.⁵

The results were fed to the General Board of the Navy. Working directly for the Secretary of the Navy and the Chief of Naval Operations (CNO), the General Board was made up of some of the most respected admirals in the Navy. It conducted frequent hearings with subject-matter experts from the fleet and the Navy’s engineering bureaus, out of which the board developed requirements for prospective platforms. It is no exaggeration to say that the World War II U.S. Navy was conceived by the General Board during the interwar period.⁶

Results also informed operational doctrine. During Fleet Problems in the 1920s, fleet commanders determined that S-boats, the largest class of U.S. submarines at the time, were too slow to keep up with the surface fleet. As a result, commanders chose to deploy the S-boats well ahead of the battle line and ordered them to attack on making contact with the enemy. When the first V-boats of the 1930s entered service, U.S. submariners experimented with subs operating together as a “battle task force” before abandoning the concept. Through experimentation, fleet exercises determined that submarine commanders should operate independently, a role subsequently written into doctrine.⁷

By March 1931, the submarine force had gained enough at-sea experience from the first six V-boats to hold a conference to refine the fleet boats’ characteristics. The conference wrote out a long list of recommendations for future submarines, with an emphasis on the independent scouting role. Submarines would need to be smaller than the first six V-boat prototypes, with a displacement that supported extended range, along with fuel, weapons, food, and supplies for at least two months of war patrol.⁸

In 1935, the Submarine Officers Conference reiterated and updated the desired characteristics, with lessons from operational experience. Submarines still needed to be small to be maneuverable, but they also required a little more space to better support long ocean voyages and carry more weapons.⁹ These characteristics would guide submarine design through the end of World War II.¹⁰

It would be difficult to overstate the value of the interwar operational feedback loop in identifying key information and converting it into updated requirements and doctrine. But even as Fleet Problems led to a doctrine of independent operations, they also left significant blind spots and misperceptions, including an exaggerated sense of vulnerability to sonar and aircraft. Worse, the operational feedback loop did not recognize that the Mk 14 torpedo and its overly complicated Mk VI magnetic exploder had been inadequately tested, costing submarines and lives in 1942 and 1943.¹¹

Incremental but Rapid Development

The strategic imperatives of War Plan Orange set the requirements for U.S. submarines, while operational feedback about what worked—and what did not—refined them. This allowed the Navy to build an advanced submarine force through innovation by junior officers, collaboration with outside industry, and a rapid but incremental development process.

Deckplate innovators proved crucial to the development of the fleet submarine. For instance, World War I and 1920s submarines launched torpedoes using compressed air, releasing bubbles that upset the submarine’s trim and gave away its position. Lieutenant Marshall M. Dana solved this problem at Portsmouth Navy Yard in the early 1930s with the “bubble eliminator,” a poppet valve that vented air and water from the torpedo tube into a tank in the torpedo room bilges.¹² 

Similarly, around 1932, Lieutenant Commander Olton Bennehoff designed and built a rudimentary torpedo data computer (TDC) while commanding the USS S-48 (SS-159). Bennehoff experienced numerous difficulties, not the least of which was that his first attempt was too large to fit through the submarine’s hatches. But he progressed enough with the concept that the Navy had him continue work on it at the Bureau of Ordnance (BuOrd). With the General Board’s blessing, BuOrd took Bennehoff’s concepts, shared them with industry, and ultimately used competition between Arma and Ford Instrument to develop a superior computer that could solve multiple equations simultaneously.¹³ No other navy developed anything comparable before or during World War II. The German and Japanese submarine fleets possessed only angle solvers for their fire-control systems.¹⁴ 

Perhaps the most important technological development in the 1930s was the tremendous improvement in submarine diesel engines, the result of collaboration with private industry. Following World War I, diesel engine reliability and efficiency were so poor that fleet commanders did not expect submarines would ever operate faster than 15 knots. Anything more appeared to require submarines of unwieldy size.¹⁵ By 1930, the Navy’s engineering bureaus were so discouraged with the state of U.S. diesel engines that they implored the General Board to purchase German diesel technology. But even after the Navy obtained German-designed M.A.N. diesels for the last two V-boats, officers remained dissatisfied with engine reliability and operation.¹⁶ 

Only a few years later, however, improvement in railroad diesel engines permitted a tremendous leap forward. The submarine force and the railroad industry cooperated to design and produce powerful new compact diesel engines that finally allowed U.S. submarines to proceed at high speed on the surface and recharge their massive battery banks. Future Admiral Stuart S. “Sunshine” Murray recalled the close collaboration between the USS Porpoise (SS-172)—the first fleet submarine with the improved engines—and the Boston and Maine Railroad: 

When we were short of spare parts, due to nonarrival or anything like that, the Boston and Maine was very helpful in that they would trade spare parts with us. We could get them right off of their diesel engines or from their diesel shops. I might add it worked the other way at times also. They borrowed from us.¹⁷

All these developments led to rapid, if incremental, changes in U.S. submarine design. Starting in 1933, with the New Deal’s financial support for industrial recovery, the Navy built small blocks of submarines every fiscal year. Each block entered the operational feedback loop immediately on acceptance into the fleet, with recommendations from engineers and submarine crews quickly fed back to the General Board and applied to the next year’s block. In this way, the Navy transitioned from the Porpoise to the Gato (SS-212) in just eight years. Although the Gato bore a superficial similarity to the Porpoise, the number of torpedoes she carried increased by almost a full third, test depth increased by a fifth, surface speed improved, and submarine equipment evolved to include torpedo data computers, air conditioning, and more.¹⁸ 

This “incrementally rapid” process continued during World War II, if anything, at a faster pace—bringing advanced radars, bathythermographs, and electronic bearing transmitters to submarines in a little more than three years.¹⁹

U.S. submarines evolved tremendously after November 1918. When war came in December 1941, a Gato-class submarine could proceed faster surfaced or submerged, go almost as far, and carried more weapons than its closest German counterpart, a Type IXB U-boat. The U-boat’s primary advantage was that it was designed to go deeper.²⁰

But a straightforward comparison of characteristics understates the Gato’s advantages. For instance, although the Type IXB U-boat carried nearly as many torpedoes as a Gato, almost half were carried externally. To use the torpedoes, the U-boat required calm seas and adequate time to unstow them, hoist them through a hatch, and strike them below. This evolution left the U-boat highly vulnerable to attack and without easy access to half its primary weapons. And while the Type IXB had a moderately longer range than its U.S. counterpart, German submarines lacked air conditioning, a crew’s mess, and other amenities that permitted extended patrols in any climate. While U.S. submarines could remain on station for two to three months and maintain adequate alertness and high battle standards, U-boat sailors were forced to endure hellish conditions of unbearable humidity and condensation, as well as soaring interior temperatures when surfaced. Consequently, the relative disparity in effectiveness of these submarines only increased with time on station.²¹

Admittedly, U.S. submarines were carrying out missions in the Pacific, not directly competing against German U-boats. But they were tremendously successful. Even though U.S. submarines were unexpectedly assigned the mission of unrestricted warfare against Japanese trade, they proved superbly capable at it, as well as at combat against Japanese fleet units and a variety of missions such as aviation lifeguard and guerrilla landings. U-boats proved much less successful at the missions the Kriegsmarine set out to accomplish.²²

Lessons for Tomorrow

The architects of tomorrow’s U.S. Navy—not only submariners—should draw a number of lessons from the successful development of the U.S. fleet submarine. 

Design platforms and payloads from a clear-eyed strategic vision. The interwar requirements for U.S. submarines were based on genuine needs to support a transpacific offensive, such as speed, range, weapons loadout, and endurance. As today’s Navy develops future warships, aircraft, and weapons, the characteristics of these platforms and payloads must be tied to the latest plans for tomorrow’s fight. Designers should set specifications and capabilities in relation to the most limiting war plan.

Frequently refine design characteristics, technology, and doctrine through operational feedback. Upgrades in submarine design, performance, and doctrine from the S-boats of the early 1920s to the Gato-class in 1941 owed much to the operational feedback loop that included Fleet Problems and the General Board. The 2016 resurrection of Fleet Problems in the Pacific Fleet is a welcome use of the past to inform the future Navy. But the interwar Navy worked as well as it did because its feedback loop included independent organizations such as the General Board, the Naval War College, various fleet elements, and the Office of the CNO. The resurrected Fleet Problems, on the other hand, appear to be an internal Pacific Fleet program.²³ Today’s Fleet Problems should be incorporated into a broader modern operational feedback loop.

Collaborate with industry. Just as yesterday’s Navy benefited from a close relationship with the railroad industry, today’s Navy needs to establish and maintain close ties with industries pursuing cutting-edge information technologies, advanced metallurgy, and sensors.

Take ideas from the deckplate. The advent of 3D printers and computer-aided design allows the Navy’s highly trained technical wizards to develop their own solutions. The Navy should reward these innovators by assigning them develop­ment duties, much as Bennehoff reported to BuOrd to supervise the refinement of his initial TDC. 

A Radical (but Historical) Solution

None of the above recommendations matter if the Navy’s acquisitions program continues to produce platforms and weapons at a snail’s pace. Countless articles criticize the long delays in producing new warships and aircraft—especially the decades-long production of the Navy’s top priority, the Columbia-class ballistic-missile submarines. With such a prolonged production line, what hope is there to improve platforms through annual incremental change?

The first 170 years of U.S. warship procurement suggest a radical solution: construction at naval shipyards. From the earliest days of the Republic through the late 1960s, government-funded and -run naval shipyards at Portsmouth, Brooklyn, Mare Island, and elsewhere designed and constructed all manner of warships. These shipyards served as a valuable foil for and competitor to private industry. 

Much of the conceptual design and testing of the fleet submarines was done at Portsmouth Naval Shipyard in Maine. (See “Midwife to the Fleet Boat,” August 2018, pp. 34–38.) After proving its competence with the L-8 (SS-48), Portsmouth became the Navy’s submarine builder of choice. When naval construction boomed during the Depression, President Franklin D. Roosevelt assigned construction to the Brooklyn Navy Yard and other government shipyards to force private shipbuilders to reduce costs. Naval leaders also recognized that there were fewer labor problems at the government yards. The public shipyards continued to prove their worth in time of crisis: Portsmouth Naval Shipyard proved to be far more efficient than others, steadily reducing construction time and building quality submarines throughout the war.²⁴

Despite this, Congress shifted all new warship construction from the naval shipyards to private shipbuilders in the late 1960s to guarantee private shipyards government business. In addition, there were claims that private industry would naturally drive down costs and seek efficiencies.²⁵

The past half-century argues that this is not the case. Indeed, Admiral Hyman G. Rickover, not always a strong advocate of Navy shipyards, grew so frustrated with private yards that he proposed shifting new construction back to public ones to provide “a benchmark to judge costs at private yards” shortly before he was forcibly retired.²⁶

Because it has been more than 50 years since a U.S. naval shipyard designed and constructed a warship, this historical solution is radical. The costs of standing up new construction capabilities might be prohibitive, but the opportunity to add competition and drive efficiencies the way that Portsmouth Naval Shipyard did in the first half of the 20th century may help break the Navy free of the current acquisition morass.

The development of U.S. submarines from inferiority at the end of one war to high quality at the start of the next offers many lessons. The leaders assigned to design and build the platforms and payloads necessary for the next war should internalize the need for clear-eyed strategic vision, build a high-velocity operational feedback loop, take advantage of the talents of the deckplate, and reform the current shipbuilding industry. The Navy can ill afford to end up with a Type IXB U-boat instead of a Gato-class fleet submarine.