Japan's Super-Torpedo Was the Hypersonic Missile of WWII

The Long Lance was a devastating weapon against U.S. warships.

When U.S. Navy warships began exploding in the middle of the night, America realized it had a problem.

In the autumn of 1942, Guadalcanal, in the Solomon Islands near Australia, became the focal point of the Pacific War. For six months, U.S. and Japanese forces savagely battled on land, air, and sea to determine who would control the island and its strategic airfield.

For the U.S. Navy, which had belittled the Japanese as incompetent, Guadalcanal came as a shock. The disaster at Pearl Harbor could be explained by surprise and treachery, but the Navy left two dozen warships in "Ironbottom Sound" off Guadalcanal.

One reason was the "Long Lance," the Japanese torpedo that was the most powerful weapon of its kind in the early years of World War II. Developed in the late 1920s, the Long Lance, as Americans nicknamed it (the Japanese designation was the "Type 93"), was a remarkable device. In modern parlance, it would be an asymmetric weapon, designed to compensate for Japanese inferiority to more economically powerful Western nations. In some ways, it was the equivalent of hypersonic ship-killing missiles that China and Russia would use to counter the superior U.S. Navy.

When the Second World War began, the Japanese plan was to exercise patience to defeat a stronger foe. Under the "decisive battle" strategy, Japan would seize the Philippines, and as the U.S. Navy sailed across the Pacific to recapture Manila, it would be harried and worn down by persistent aircraft, submarines and destroyer attacks. Once the American battle fleet had been sufficiently weakened, the Japanese battle fleet would sortie out and sink it in a huge Jutland-style naval battle near the Philippines.

To accomplish this, the Imperial Japanese Navy relentlessly trained its surface ships in night torpedo attacks that would allow its ships to sneak up on and destroy the enemy. The Imperial Navy lacked radar, but lookouts were rigorously trained and equipped with powerful night binoculars. Yet all would be for naught without a good torpedo, and the Long Lance more than met the need.

The Long Lance was a big torpedo for its time, some two feet in diameter, almost thirty feet long and weighing almost three tons. It was armed with a 1,080-pound warhead that was 50 percent larger than most other torpedo warheads. Most important was the Long Lance's propulsion system. Most other nations fielded torpedoes propelled by steam, diesel or electric propulsion. But the Japanese opted for a pure oxygen-based system (inspired by an earlier British design) that could send the Long Lance out to twelve miles at a speed of 48 knots, or an incredible 24 miles—about the same range as a battleship's gun—at a speed of 36 knots. The Long Lance also didn't leave telltale bubbles on the surface to warn enemy ships a torpedo was approaching.

How did this compare to U.S. torpedoes? The 21-inch-diameter Mark 15, carried by U.S. destroyers, weighed less than two tons and only hefted an 825-pound warhead. Worst of all, its maximum range was only eight miles, or one-third that of the Long Lance. Not surprisingly, the Americans emphasized naval guns rather than torpedoes.

The Americans quickly felt the sting of the Long Lance. At the Battle of Savo Island, a task force of Japanese heavy cruisers (the Americans wouldn't have dreamed of using  heavy warships in a night torpedo attack) and destroyers surprised an Allied force, sinking three American and one Australian heavy cruiser. The subsequent withdrawal of the U.S. Navy nearly doomed the U.S. Marine garrison on Guadalcanal. At the Battle of Tassafaronga on the night of November 30, 1942, the Imperial Navy's "Tokyo Express" force of destroyers sank one and badly damaged three U.S. Navy heavy cruisers, at a cost of just one destroyer.

The problem wasn't just the Long Lance. It was also superiority of Japanese sensors, namely the Mark I human eyeball. The U.S. Navy placed its faith in newly developed radar for surface ships, but the primitive radar of late 1942 was unreliable and its operators inexperienced. Japanese lookouts consistently spotted U.S. ships first at incredible ranges. Once spotted, Imperial cruisers and destroyers could launch torpedoes that unlike naval guns, betrayed neither flash nor sound, thus preserving the element of surprise while denying the enemy a target.

Yet lest the Long Lance become a symbol of technological triumphalism, or a prequel to what China and Russia hope their missiles will do to American carriers, it is important to remember that Japan ultimately lost Guadalcanal. The Japanese edge eroded as American radar, crew experience and tactics improved. During the actions around the Second Naval Battle of Guadalcanal in November 1942, Japan lost two battleships and other vessels.

The Long Lance was a devastating weapon, but only at a given time and under a unique set of conditions: Primitive U.S. radar versus sharp-eyed Japanese lookouts, inexperienced American crews pitted against well-trained Japanese sailors, poor U.S. tactics contrasted with Japanese night fighting expertise, and close-quarters surface combat in confined island waters.

Pages