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All this U.S. submariners accomplished with inferior equipment. Torpedoes often failed to explode after a direct hit, many ran too deep, the boats were too thin-skinned to dive much beyond 300 feet. Identification systems were poor (two U.S. subs were almost certainly sunk by U.S. planes). Subs could cruise only at two or three knots submerged.
Snorkels & Figure Eights. The Germans, the Navy discovered after the war, had done much better in submarine design. After V-E day, the U.S. had gotten two grimy, eerie-looking Nazi XXI U-boats that made U.S. subs as obsolete as the first chugging steel cigar delivered to the Navy by John P. Holland in 1900. Luckily, only a few of those Nazi subs got into operation. With U.S. crews aboard, the German XXIs sliced underwater at 16 knots. They had snorkel tubes, long-range homing and pattern-running torpedoes that swept through convoys in figure-eights. They had periscopes and sonar (sound navigation and ranging) listening devices superior to anything the U.S. had.
All too slowly, the Navy started grafting the German inventions on to its own 76 active subs (another 91 were in mothballs). It spent $175 million on its modernization program, called the refitted subs "guppies" and sent them out to see what they could do. They couldn't quite match the German XXIs, but even so the results were astounding. The snorkel tube, the Navy found, made a sub 16 times as effective. The U.S.S. Pickerel, a guppy type, traveled 5,200 miles across the Pacific in 21 days without surfacing. On maneuvers, the Amberjack swept through the fleet, "sank" 250,000 tons of shipping before being caught.
Sub v. Sub. Guppies have also revolutionized antisubmarine warfare. The men who man them boast that it takes three destroyers to kill a sub; one destroyer alone would fall victim to a guppy. The Tang class, entirely new subs built on the German XXI model, would be even tougher. In any future war, submen argue, it may take a sub to kill a sub, a process which Rear Admiral Charles Momsen describes as like "two blindfolded antagonists armed with baseball bats, each waiting for the other to break silence."
Unfortunately, the Russians also got hold of the German XXI after the war—not just two but a fleet of more than 25 of them, and parts for many more. Still worse, they walked off with an even more fearsome sub which the Germans had on the ways as the war ended. Called the XXVI, it is the first true underwater craft ever built. For long stretches at a time, it needs no snorkel tube to suck air down to its engines, but runs entirely submerged on a new type of engine in which hydrogen peroxide is used to oxidize the fuel. It can swim full speed on engines at its maximum depth. The U.S., though it knows how the XXVI works, never got one of them. The Russians captured the whole business—enough parts and prefabricated sections to build 75 XXVis, and enough German scientists and submen to show them how to run them.