Gato-class submarine

The United States Navy Gato-class submarine formed the majority of the United States Navy's World War II submarine fleet. Named after the first vessel of this design, USS Gato (SS-212), the Gato-class and its successors, the Balao and Tench classes, formed the core of the submarine service that was largely responsible for the destruction of the Japanese merchant marine and a large portion of the Imperial Japanese Navy in World War II. Gato's name comes from a species of small catshark. Like most other U.S. Navy submarines of the period, the Gato-class were given the names of marine creatures.

Design
The Gato-class boats were considered to be "Fleet Submarines". The original rationale behind their design was that they were intended to operate as adjuncts to the main battle fleet. They were to scout out ahead of the fleet and report on the enemy fleet's composition, speed, and course, then they were to attack and whittle down the enemy in preparation for the main fleet action, a titanic gun battle between cruisers and battleships. This was an operational concept borne out of experience from World War I. In order to operate effectively in this role, a submarine had to have high surface speed, long range and endurance, and a heavy armament. State-of-the-art submarine design and construction in the 1920s and 1930s made this combination of qualities very difficult to achieve. The USN constantly experimented with this concept in the post-World War I years, producing a series of submarines with less than stellar qualities and reliability, the T class and the so-called V boats.

By 1931, the experimental phase of fleet submarine development was over and the Navy began to make solid progress towards what would eventually be the Gato-class. By 1940, a much better developed industrial base and experience gained from the Porpoise-, Salmon-, & Sargo-class boats resulted in the Tambor- & Gar-classes. Finally, the USN had hit the right combination of factors and now had the long-desired fleet submarine.

Timing, however, conspired against the actual use of these boats in their assigned role. The attack on Pearl Harbor on 7 December 1941 destroyed the Pacific Fleet battle line and along with it the concept of the battleship-led gun battle. The successful Pearl Harbor attack overturned 20 years of submarine strategic concept development and left the fleet submarine without a mission. Fortunately, the very same capabilities that would have enabled these submarines to operate with the fleet made them superbly qualified for their new mission of commerce raiding against the Japanese Empire

The Gato-class design was a near duplicate of the preceding Tambor- & Gar-class boats. The only significant difference was five feet in length added to the engine room section to allow the addition of a watertight bulkhead, dividing the one large engine room in two, with two diesel generator sets in each room. The Gatos, along with nearly all of the USN fleet-type submarines of World War II were of partial double hull construction. The inner pressure-resisting hull was wrapped by an outer hydrodynamic hull. The void areas between the two hulls provided space for fuel and ballast tanks. The outer hull merged with the pressure hull at both ends in the area of the torpedo room bulkheads, thus the "partial" double hull. Operational experience with earlier boats led the naval architects and engineers at the Navy's Bureau of Construction & Repair to believe that they had been overly conservative in their estimates of hull strength. Without changing the construction or thickness of the pressure hull steel, they decided that the Gato-class boats would be fully capable of routinely operating at 300 feet, a 50-foot increase in test depth over the preceding classes.

The Gatos were slow divers when compared to some German and British designs, but that was mostly because the Gatos were significantly larger boats. Sufficient fuel bunkerage to provide the range necessary for 75-day patrols from Hawaii to Japan and back could only be obtained with a large boat, which will take longer to submerge than a smaller one. Acknowledging this limitation, the Bureau designers incorporated a negative (sometimes called a "down express") tank into the design which provided a large amount of negative buoyancy at the start of the dive. Normally kept full or nearly full at the surface, the tank was emptied to a certain mark after the boat was submerged to restore neutral buoyancy. At the start of the war these boats could go from fully surfaced to periscope depth in approximately 45–50 seconds. The superstructure that sat atop the pressure hull provided the main walking deck when the boat was surfaced and was free flooding and full of water when the boat was submerged. When the dive began the boat would "hang" for a few extra seconds while this superstructure filled with water. In an attempt to speed this process, additional limber, or free flooding, holes were drilled and cut into the superstructure to allow it to flood faster. By mid war, these measures combined with improved crew training got dive times down to 30–35 seconds, very fast for such a large boat and acceptable to the boat's crew.

The large size of these boats did negatively impact both surfaced and underwater maneuverability when compared to smaller submarines. There was no practical fix for this due to the limitations of the installed hydraulic systems that were used to move the rudder. Although a point of concern, turning radius was still good enough to be acceptable. After the war, a few fleet boats were fitted with an additional rudder topside at the very stern.

These boats all had air conditioning, refrigerated storage for food, fresh water distilling units, clothes washers, and bunks for nearly every crew member; luxuries virtually unheard of in other navies. The Bureau designers felt that if a crew of 60–80 men were to be expected to conduct 75-day patrols in the warm waters of the Pacific, these types of features were vital to the health and efficiency of the crew. They could be added without impact to the boat's war fighting abilities due to the extra room of the big fleet boat. However, one feature in particular had a very practical side to it. Submerge a submarine for any length of time and the heat generated by the recently shut down engines, electronic gear, and 70 warm bodies will quickly raise internal temperatures above 100 Fahrenheit. High humidity generated by tropical waters will quickly condense and begin dripping into equipment, eventually causing electrical shorts and fires. Air conditioning, acting mostly as a dehumidifier, virtually eliminates this problem and greatly increases mechanical and electrical reliability. It proved to be a key factor in the success of these boats during World War II.

Twelve submarines of this class built by Electric Boat received what would be the final installations of the Hooven-Owens-Rentschler (HOR) double acting diesel engine. The Navy had been tinkering with this engine off and on since 1937 because its unique design promised nearly twice the horsepower in a package the same size as other diesel engine types. Unfortunately, the HOR company ran into severe design and manufacturing problems and these engines proved to be operational and maintenance nightmares. Frequent breakdowns and utter unreliability had destroyed these engines' reputation with the Navy and they were all removed at the first opportunity and replaced by GM-Winton 16-278A V-type diesels. The other Gato-class boats received either the Fairbanks-Morse 38D8 1/8 nine cylinder opposed piston engine or the GM-Winton 16-248 V-type as original installations. These engines were hardy, rugged and well liked by the crews and served the boats quite well.

World War II


These boats were authorized in appropriations for Fiscal Year 1941, as part of President Franklin Roosevelt's proclamation of "limited emergency" in September 1939. The first boat laid down was actually the USS Drum (SS-228) at Portsmouth Naval Shipyard on 11 September 1940. She was commissioned on 1 November 1941 and was the only Gato-class boat in commission when the war started. The Gato herself was laid down on 5 October 1940 by the Electric Boat Company at Groton, Connecticut and commissioned 31 December 1941. Due to their large construction capacity, more than half (41) of the class was built at Electric Boat facilities; three new slipways were added to the north yard and four slipways were added to the south yard to accommodate their production. In addition, the government purchased an old foundry downstream from the main yard, constructed ten slipways and turned the yard over to Electric Boat. Called the Victory Yard, it became an integral part of Electric Boat operations. A total of 77 Gatos were built at four different locations (Electric Boat, Manitowoc, Portsmouth, and Mare Island).

There is occasionally some confusion as to the number of Gato-class submarines built with some sources listing the total as 73. This is due to the transitional nature of the first four boats (SS-361 to SS-364) constructed under the second contract by the Manitowoc Shipbuilding Company of Manitowoc, Wisconsin. These were originally intended to be Balao-class subs and were assigned numbers that fall in the middle of the range of numbers for the Balao-class (SS-285 to SS-416 & 425–426). Manitowoc was a designated follow-on yard to Electric Boat; they used construction blueprints and plans supplied by Electric Boat and used many of the same suppliers. The government-owned shipyards (Portsmouth Naval Shipyard and Mare Island Naval Shipyard) began to make the transition to the new Balao design in the summer of 1942. Electric Boat, due to the huge backlog of Gato-class construction, was not ready to make the transition to the new design until January 1943. Manitowoc had already completed their allotted production run of Gatos and could not switch over to the Balao design until Electric Boat supplied them with the plans. Faced with a work stoppage while they waited for Electric Boat to catch up, managers at Manitowoc got permission to complete four additional boats (SS-361 to SS-364) to Electric Boat's Gato-class plans. Manitowoc's first Balao-class boat was USS Hardhead.

All of the Gatos (with one exception, USS Dorado) would eventually fight in the Pacific Theater of Operations. However, in the summer of 1942, six brand new Gatos were assigned to Submarine Squadron 50 and sent to Rosneath, Scotland to patrol the Bay of Biscay and to assist in the Operation Torch landings in North Africa. All in all they conducted 27 war patrols but could not claim any verified sinkings. Considered a waste of valuable resources, in mid 1943 all six boats were recalled and transferred to the Pacific.

Once they began to arrive in theater in large numbers in mid-to-late 1942, the Gatos were in the thick of the fight against the Japanese. Many of these boats racked up impressive war records. Flasher, Rasher, and Barb were the top three scoring boats in terms of tonnage sunk by US submarines. Silversides, Flasher, and Wahoo were 3rd, 4th, and 7th place on the list for the number of ships sunk. Gato-class boats sank four Japanese submarines: I-29, I-168 and I-351 and I-42; while only losing one in exchange, USS Corvina (SS-226) to I-176.

Their principal weapon was the steam powered Mark 14 torpedo in the early war years, with the electric Mark 18 torpedo supplementing the Mark 14 in late 1943. Due to a stunted research and development phase in the Depression era 1930s, and in great part due to the arrogance and stubbornness of the Navy's Bureau of Ordnance, the "wonder weapon" Mark 14 proved to be full of bugs and very unreliable. They tended to run too deep, explode prematurely, run erratically, or fail to detonate. Bowing to pressure from the submariners in the Pacific, the Bureau eventually acknowledged the problems in the Mark 14 and largely corrected them by late 1943. The Mark 18 electric torpedo was a hastily copied version of captured German G7e weapons and was rushed into service in the fall of 1943. Unfortunately it too was full of faults, the most dangerous being a tendency to run in a circular pattern and come back at the sub that fired it. Once perfected, both types of torpedoes proved to be reliable and deadly weapons, allowing the Gatos and other submarines to sink an enormous amount of Japanese shipping by the end of the war.

The Gatos were subjected to numerous exterior configuration changes during their careers, with most of these changes centered on the conning tower fairwater. The large bulky original configuration proved to be too easy to spot when the boat was surfaced; it needed to be smaller. Secondly, the desire to incorporate new masts for surface and air search radars drove changes to the fairwater and periscope shears. Third, additional gun armament was needed and cutting down the fairwater provided excellent mounting locations for machine guns and anti-aircraft cannon. The modifications (or Mods) to the Gato-class conning tower fairwaters were fairly uniform in nature and they can be grouped together based on what was done when:
 * Mod 1 – This is the original configuration with the covered navigation bridge, the high bulwark around the aft "cigarette" deck, and with the periscope shears plated over. All the early boats were built with this Mod and it lasted until about mid 1942.
 * Mod 2 – Same as Mod 1 but with the bulwark around the cigarette deck cut down to reduce the silhouette. This also gave the .50 caliber machine gun mounted there a greatly improved arc of fire. Began to appear in about April 1942.
 * Mod 3 – Same as Mod 2 but with the covered navigation bridge on the forward part of the fairwater cut away and the plating around the periscope shears removed. In this configuration the Gatos now had two excellent positions for the mounting of more powerful 20 mm anti-aircraft cannon. This mod started to appear in late '42 and early '43.
 * Mod 4 – Same as the Mod 3 but with the height of the bridge itself lowered in a last attempt to lessen the silhouette. The lowering of the bridge exposed three I-beams on either side of the periscope shears. These exposed beams gave rise to the nickname "covered wagon boats". Began to appear in early 1944.

Variations on the above mods included the 1A (shortened navigation bridge), 2A (plating removed from periscope shears), and the 3A and 4A (which moved the SJ radar mast aft of the periscopes).

A Japanese boarding party from the destroyer JAPANESE DESTROYER Naganami inspected the grounded and abandoned USS Darter (SS-227). Documents disclosed weaknesses, later used to improve Japan's anti-submarine warfare.

Notable successes

 * USS Albacore (SS-218) sank the Japanese aircraft carrier Taiho. Taiho was the flagship of Vice-Admiral Jisaburo Ozawa's fleet during the Battle of the Philippine Sea.
 * USS Barb (SS-220), on her 12th patrol in July 1945, landed a small team from her crew on the shore of Patience Bay on Karafuto. They placed charges under a railroad track and blew up a passing train. The Barb also conducted several rocket attacks against shore targets on this same patrol, the first ever by an American submarine. They used 5-inch unguided rockets fired from a special launching rack on the main deck.
 * USS Cavalla (SS-244) sank the Japanese aircraft carrier Shokaku. Shokaku was one of six Japanese carriers that had participated in the attack on Pearl Harbor.
 * USS Cobia (SS-245) sank a ship carrying Japanese tank reinforcements which were en route to Iwo Jima.
 * USS Cod (SS-224) went to the rescue of a grounded Dutch submarine O-19, taking its crew on board and destroying the submarine when it could not be removed from the reef, the only international submarine-to-submarine rescue in history.
 * USS Corvina (SS-226) was the only U.S. submarine sunk by a Japanese submarine (I-176) during the Second World War.
 * USS Finback (SS-230) recovered downed pilot LTJG George H. W. Bush, future President of the United States, after his TBM Avenger bomber was damaged and eventually ditched during a bombing mission at Chichi-jima in the Pacific.
 * USS Flasher (SS-249) was the top-scoring U.S. boat of the war, with 100,231 tons officially credited to her by the Joint Army-Navy Assessment Committee JANAC.
 * USS Growler (SS-215)'s skipper, Howard W. Gilmore, earned the submarine force's first combat Medal of Honor for sacrificing his life to save his boat and his crew. Alone on the bridge after being wounded by enemy gunfire, and unable to reach the hatch after he had ordered the others below, he pressed his face to the phone and uttered the order that saved his boat and sealed his doom: "Take 'er down!"
 * In USS Grunion (SS-216), Mannert L. Abele earned the submarine force's first Navy Cross, when his boat engaged in a running battle with Japanese ships off Kiska in July 1942. Grunion was subsequently lost in this action. In 2006 and 2007, expeditions organized and led by Abele's sons, Bruce, Brad, and John, located and photographed the wreck of the Grunion using side scan sonar and a remotely operated vehicle (ROV).
 * USS Harder (SS-257) was commanded by Samuel D. Dealey, the only submarine commander of the war (perhaps the only one ever) to sink five enemy destroyers, four in a single patrol.
 * USS Mingo (SS-261), which sank two Japanese ships during her patrols, was lent to the Japanese Maritime Self Defense Force after the war, serving under the name Kuroshio.
 * USS Trigger (SS-237) became famous in Edward L. "Ned" Beach's book Submarine! (which was a kind of eulogy to her).
 * USS Tunny (SS-282) sank the Japanese submarine I-42 on the night of March 23, 1944, after the two subs dueled for position for over an hour. A week later Tunny engaged the battleship Musashi but only slightly damaged her with a torpedo to the bow.
 * USS Wahoo (SS-238), commanded by the submarine force's most famous skipper, Dudley W. "Mush" Morton, engaged in a running gun and torpedo battle with a convoy of four ships off the coast of New Guinea and destroyed the entire convoy. She was also one of the first U.S. subs into the Sea of Japan. She was sunk while exiting the Sea of Japan through the La Perouse Strait in October 1943 while on her seventh patrol.
 * USS Darter (SS-227) along with USS Dace (SS-247) conducted an aggressive and successful attack against Japanese fleet units during the lead up to the U.S. invasion of Leyte Island in the Philippines in October 1944. The two boats sank the heavy cruisers Atago and Maya and severely damaged the heavy cruiser Takao. A few hours later, while maneuvering back to the scene to finish off the crippled Takao, Darter ran hard aground on Bombay Shoal off Palawan. Her entire crew was rescued and subsequent attempts to destroy the wreck were only partially successful, and the Japanese successfully obtained important documents to exploit weaknesses on the class' hull. As late as 1998, portions of Darter's hulk were still visible on the reef.
 * USS Halibut (SS-232) was essentially the 53rd U.S. submarine loss of the war. Terribly damaged in an aircraft borne depth charge attack on 14 November 1944, she barely limped back to port in Saipan. Temporarily patched up, she was sent back to the states. Examined by engineers, she was found to be beyond economical repair and was decommissioned on 18 July 1945, never having made another war patrol. Her entire crew survived.

Medal of Honor awards

 * USS Barb (SS-220) • Eugene B. Fluckey
 * USS Growler (SS-215) • Howard W. Gilmore
 * USS Harder (SS-257) • Samuel D. Dealey

Postwar service
At the end of World War II, the USN found itself in an awkward position. The 56 remaining Gato-class submarines, designed to fight an enemy that no longer existed, were largely obsolete despite the fact they were only two to four years old. Such was the pace of technological development during the war that a submarine with only a 300-foot test depth was going to be of little use, despite being modern in most other aspects. There were enough of the Balao and Tench boats, with their greater diving depth, that the Gatos were superfluous for front line missions. The Guppy modernization program of the late 1940s largely passed these boats by. However, the USN found itself new missions to perform and for some of these the Gatos were well suited. The last two Gato-class boats active in the US Navy were the Rock and the Bashaw which were both decommissioned on 13 September 1969 and sold for scrap.

Radar picket
The advent of the Kamikaze demonstrated the need for a long range radar umbrella around the fleet. Surface ships refitted with powerful radar suites were put into service, but they proved vulnerable in this role as they could be attacked as well, leaving the fleet blind. A submarine though, could dive and escape aerial attack. After experimenting with the concept on several Balao- and Tench-class boats, and realizing that a deep diving depth was not overly important in this role, six Gatos were taken in hand (Pompon, Rasher, Raton, Ray, Redfin, & Rock) for conversion. They were lengthened by 24 feet to provide additional space for an air control center and had powerful air search and height finding radars installed. They also received a streamlined "sail" in place of the traditional conning tower fairwater. Redesignated SSR and called the "Migraine III" conversion, these boats were only moderately successful in this role as the radars themselves proved troublesome and somewhat unreliable. The radars were removed and the boats temporarily reverted to general purpose submarines after 1959.

Hunter-killer
The increasing threat of Soviet submarines in the Atlantic led the USN to adapt submarines to specifically hunt other submarines, a radically new role for the 1950s. Concluding that this role did not require a fast or deep diving submarine (this line of thought would quickly change with the advent of nuclear power), seven Gatos were converted to SSK's between 1951 and 1953. A streamlined Guppy style sail was installed, a large sonar array was wrapped around the bow (losing two torpedo tubes in the process), the boats were extensively silenced, and they received a snorkel. USS Grouper (SS-214) was the test boat for the concept, having her sonar array at the forward end of the sail instead of the better position at the bow. The other boats in the program included Angler, Bashaw, Bluegill, Bream, Cavalla, and Croaker. Technological advances in sonars allowed them to be installed on all of the new nuclear boats and the SSK mission was folded into the regular attack submarine role. These slow and less capable boats were decommissioned and scrapped in 1968 and 1969.

Guided missile submarine
The Regulus nuclear cruise missile program of the 1950s provided the USN with its first strategic strike capability. Tunny was converted in 1953 to house and fire this large surface-launched missile and was designated SSG. She could carry two of the missiles in a cylindrical hangar on the aft deck. She made strategic deterrence patrols with Regulus until 1964, when the program was discontinued in favor of Polaris. Tunny was subsequently converted into a troop transport, her Regulus hangar becoming a lockout chamber for UDT and SEAL teams. In this role she was designated an LPSS.

Submarine oiler
Guavina was converted to a SSO in 1950 to carry fuel oil, gasoline, and cargo to amphibious beachheads. She received additional "saddle" tanks wrapped around her outer hull to carry these fuels and a streamlined sail. After a few tests the concept was dropped in 1951 as impractical and Guavina served in the test role for a few years. In 1957 she converted back to the oiler/tanker role and carried the designation AOSS. This time she experimented with refueling seaplanes at sea, but this mission too was dropped after a few years and Guavina was decommissioned.

Sonar test boat
The development of advanced sonar systems took on a great deal of importance in the 1950s and several fleet boats were outfitted with various strange-looking sonar transducer arrays and performed extensive tests. Two Gatos, Flying Fish and Grouper (previously the prototype hunter-killer boat) were assigned to these duties and proved to be key players in the development of new sonar capabilities. Grouper had all her forward torpedo tubes removed and the space was used as berthing for technicians and as a sonar lab. Flying Fish was decommissioned in 1954, but Grouper continued in the test role until 1968.

Naval Reserve trainer
Interested in maintaining a ready pool of trained Reservists, the Navy assigned numerous fleet boats to various coastal and inland ports (even in Great Lakes ports like Cleveland, Detroit, and Chicago), where they served as a training platform during the Reservist's weekend drills. 28 Gato-class boats served in this capacity, some as late as 1971. In this role, the boats were rendered incapable of diving and had their propellers removed. They were used strictly as pierside trainers.

Foreign service
The large numbers of relatively modern, but surplus U.S. fleet submarines proved to be popular in sales, loans, or leases to allied foreign navies. While most of these boats were of the more capable Balao- and Tench-classes, some Gatos went overseas as well. Italy received two (Barb & Dace), which received the only Guppy conversions given to Gato-class boats (Guppy 1B). Japan received one (Mingo), Brazil two (Muskallunge & Paddle), Greece two (Lapon & Jack), and Turkey two (Guitarro & Hammerhead). The boats transferred to Japan and Brazil did not receive any modernizations (streamlining and snorkels) prior to transfer, but the four boats sent to Greece and Turkey did receive snorkels and partial streamlining to the fairwater.

Museum boats
Six Gatos are on display in the United States:
 * USS Cavalla (SS-244) is at Seawolf Park near Galveston, Texas (in SSK configuration)
 * USS Cobia (SS-245) is at the Wisconsin Maritime Museum
 * USS Drum (SS-228) is at Battleship Memorial Park in Mobile, Alabama
 * USS Cod (SS-224) is on display in Cleveland. It does not have doors cut through its pressure hull nor stairwells added.
 * USS Croaker (SS-246) is on display in Buffalo, New York (in SSK configuration)
 * USS Silversides (SS-236) is on display in Muskegon, Michigan