Gato-class Submarine

The United States had to build its submarines for a very particular war. Any conflict with Japan would be fought across the staggering distances of the Pacific, where a submarine might have to steam thousands of miles from Pearl Harbor or Australia simply to reach its patrol area, then remain on station for weeks. What the US Navy needed was not a coastal boat but a true “fleet submarine” — long-ranged, seaworthy, fast on the surface and able to keep its crew fit and fighting through patrols of two months or more.

The answer matured in the Gato class and its near-identical successors, the Balao and Tench classes. Entering service from 1941, these big, capable boats — built in their hundreds by yards like Electric Boat, Portsmouth and Manitowoc — became the standard American submarine of the war and the instrument of one of the most decisive campaigns of the entire conflict.

The fleet boats were superb long-range submarines. Diesel-electric like all their contemporaries, they could make over 20 knots on the surface and carried fuel for patrols of 11,000 nautical miles or more, ranging the breadth of the Pacific. Their punch was formidable: ten 21-inch torpedo tubes — six in the bow, four in the stern — with around two dozen torpedoes, plus a deck gun for finishing off smaller ships on the surface.

Crucially, they were built to keep their crews effective over enormous distances. American fleet boats were air-conditioned — a near-unimaginable luxury to a German U-boat crew — with good habitability, refrigerated stores and reliable machinery, so that a crew of around seventy could fight hard at the end of a sixty-day patrol. Later boats carried excellent radar that made them deadly hunters by night.

There was one grievous early flaw: the standard Mark 14 torpedo was plagued by defective depth-keeping and faulty detonators, and for much of 1942–43 American submariners watched perfectly-aimed torpedoes run too deep or fail to explode. Once these scandals were finally corrected, the fleet boats became one of the most effective weapons of the war.

Japan, like Britain, was an island empire utterly dependent on the sea — its war economy relied on oil, ore and food carried in merchant ships from its conquests in the south. The US submarine force set out to sever those arteries, and despite making up only a small fraction of the navy, it succeeded with devastating completeness.

American fleet boats sank well over half of all Japanese merchant tonnage lost in the war, sending the empire's tankers and freighters to the bottom faster than they could ever be replaced. By 1944–45 Japan's industry was starved of oil and raw materials, its fleet immobilised in port for want of fuel — a slow strangulation that crippled the Japanese war effort as surely as any battle. The boats also sank a host of warships, including, in one celebrated feat, the giant carrier Shinano by USS Archerfish.

The fleet boats ranged across the entire Pacific, from the home waters of Japan to the Indonesian oil routes. Famous boats and skippers became legends of the “Silent Service”: USS Tang under Richard O'Kane, the most successful American submarine of the war; USS Wahoo under the aggressive “Mush” Morton; and USS Flasher, which sank the greatest tonnage of all.

Their achievement was strategic, not merely tactical. By 1945 American submarines — the Gato and its near-sisters at the forefront — had strangled Japan, sinking well over half of all the merchant shipping the enemy lost and cutting the home islands off from the oil, ore and food of their conquered empire. A force that was a small fraction of the US Navy accounted for a vast share of what it destroyed.

Beyond sinking ships, the boats performed vital and varied service: lifeguard duty, rescuing downed airmen from the sea (among them a young naval aviator, the future president George H. W. Bush), reconnaissance, minelaying and landing special forces. Late in the war they too hunted in coordinated groups, the American answer to the German wolfpack.

Victory came at a hard price. The submarine service suffered the highest casualty rate of any branch of the US armed forces — fifty-two boats were lost with most of their crews — yet this was a fraction of the catastrophic losses suffered by the German U-boat arm, a measure of how much more favourable the balance of the Pacific submarine war proved to be.

The Gato-class fleet boat and its sisters waged one of the most quietly decisive campaigns of the Second World War. Where the German U-boats nearly severed Britain's lifeline and failed, the American fleet boats succeeded against Japan — strangling the island empire's economy, immobilising its fleet and helping bring it to the brink of collapse before the first atomic bomb fell.

Long-ranged, habitable, well-armed and, once their torpedoes were fixed, superbly effective, the fleet boats were a near-perfect tool for the war they had to fight. With over 200 built and a record out of all proportion to their numbers, they remain the unsung victors of the Pacific — the “Silent Service” that won a campaign few at home ever saw.

• Roger Chesneau (ed.), Conway’s All the World’s Fighting Ships 1922–1946 (Conway Maritime Press).
• Norman Friedman, U.S. Submarines Through 1945: An Illustrated Design History (Naval Institute Press).
• Theodore Roscoe, United States Submarine Operations in World War II (Naval Institute Press).