The Gato-Class Submarine of World War II - As early as 1620, inventors were experimenting with the concept of submersibles.

Early designs were little more than novelties, and it would take centuries of technological maturation before submarines fully came into their own.

Even limited by the technology of the time, early designers saw their usefulness in naval conflicts. The Turtle, built by David Bushnell, was used in an attempt to destroy British ships on blockade during the American Revolutionary War. 

It was not until the First World War that submarines would see widespread military use when German U-Boats began pursuing a policy of unrestricted submarine warfare against Allied merchant shipping.

Driven by new diesel-electric technologies, these vessels proved deadly against unprotected merchantmen. 

Prelude to Gato-Class 

The interwar years saw continued development; however, in the U.S., naval planners envisioned a different role for submarines instead of the Guerre de Course, or commerce raiding, practiced by the German U-boats. Instead, they would create “fleet submarines.”

These submarines were designed around the Mahanian doctrine, a concept delineated by Alfred Thayer Mahan, an American naval officer whose theories had come to dominate Naval thinking at the end of the 19th and into the early 20th century. When it came to tactics, he espoused the idea of a strong and concentrated fleet force sent to draw out the enemy fleet into a single, decisive battle with the two lines of capital ships - battleships and cruisers - duking it out until one side emerged triumphant. 

In such a fleet engagement, naval planners envisioned fleet submarines as scouts who would sortie ahead of the main force to identify the enemy fleet, then harry and harass them, sinking as many as possible before the final climactic showdown between fleets. To accomplish this mission, the subs would need a combination of speed, range, and armament, which was difficult to accomplish with the technology of the 1920s and ‘30s.

Continuous tinkering eventually led by 1940 to the Tambor and Gar classes of submarines, the direct predecessors of the Gato class. 

Gato Submarines Come to the Forefront

December 7th, 1941, changed the course of the Gatos’ future. The Japanese attack on Pearl Harbor destroyed the majority of the U.S. Navy’s main battle line and thus rendered the concept of fleet submarines obsolete. Realistically, the Mahanian concept of a major set-piece naval battle was already on the way out with the rise of the aircraft carrier as demonstrated by the Battles of Coral Sea and Midway; however, the U.S. had to decide what to do with its Gato class subs. 

Fortunately, the range, speed, and firepower baked into their designs made them perfect for raiding Japanese merchant shipping. A massive expansion of shipbuilding at the Electric Boat Yards in Groton, Connecticut, resulted in 77 Gatos being built before the war’s end from just a single boat being in commission when war broke out. 

Design, specs and capabilities:

The Gato-class grew directly out of the preceding Gar and Tambor classes.

They were five feet longer to accommodate an additional bulkhead in the engine room and had an increased diving depth of 300 feet.

Notably, the depth increase was not due to changes in design or materials. Rather, naval architects and engineers reviewed operational data from other subs and concluded the original 250 maximum depth was too conservative.

Gatos were designed with partial double-hulls: an inner, pressure hull bore the loads when diving while the outer hull provided hydrodynamic streamlining to improve speed. The space between the hulls was filled with fuel and ballast tanks. The extra fuel was essential to conduct patrols from Hawaii to Japan and back. 

The length of these patrols, 75 days, combined with the relatively large space the Gatos afforded designers allowed them to incorporate many features not found on contemporary subs. There were almost enough bunks for every crew member, which minimized “hot racking” or sharing a berthing. Furthermore, the boats had showers, refrigerators, and, most importantly, air conditioning. While these comforts were initially to sustain the crew on their long patrols, the air conditioning proved essential at dehumidifying the boat, particularly on sudden dives when the combination of hot machinery and close quarters could swiftly increase the temperature to over 100º F. 

A drawback of the increased size of the Gatos was their relatively long time to dive. In particular, the large fairwater, the sail on modern subs, was designed to flood when diving. The large air pocket it created could cause the boat to “hang” at the beginning of the dive. Over the course of the war, more holes were drilled into the fairwater to help improve dive speed. This, coupled with other reductions of the structure to reduce visibility, house new radars, and mount different guns, reduced the bubble effect of the fairwater.

By the end of the war these measures, along with crew training and experience, had reduced dive times by 15-20 seconds. 

Operational history:

The vast amount of Japanese merchant traffic in the Pacific, coupled with anemic efforts by the Imperial Japanese Navy to protect their convoys, allowed the Gatos to rack up significant sinkings. Three Gatos were among the top five of total tonnage sunk by a single submarine, and two more were in the top five of total ships sunk. One sub, Flasher, made both lists, sinking the second most tonnage and the third most number of ships. Of the nine Japanese carriers sunk by subs during the war, Gatos claimed five. 

At the war's end, the U.S. Navy had many Gatos and no idea what to do with them. Rapid technological advances had already begun rendering these boats obsolete in many ways. Attempts were made to modernize a few with newer propulsion systems, but these were soon scrapped. One boat, the Tunny, was one of the first submarine nuclear missile platforms, carrying Regulus nuclear cruise missiles; however, this concept was soon scrapped in favor of ballistic missiles. Other Gatos were tested as refuelers or used to develop burgeoning sonar designs, but all were decommissioned by the 1970s, having served their country well.

About the Author

Maya Carlin is an analyst with the Center for Security Policy and a former Anna Sobol Levy Fellow at IDC Herzliya in Israel. She has by-lines in many publications, including The National Interest, Jerusalem Post, and Times of Israel. You can follow her on Twitter: @MayaCarlin.