During World War II, the U.S. Navy had some of the most advanced weapons available, like artillery shells with proximity fuses that detonated at set distances from their target. But they also had a secret weakness: Many of their torpedoes would explode too early, would swim under their targets without exploding, or might even circle back around to hit them.
Submarine officers and representatives of the U.S. Navy Bureau of Ordnance pose with a Mk. 14 torpedo in 1943.
It wasn’t the only flawed torpedo, but most of the Navy’s torpedo problems centered around the Mk. 14. It was supposed to be the most advanced and deadly anti-ship weapon in the U.S. fleet. They ran on steam and could travel over five miles and hit speeds of almost 53 mph and then detonate under an enemy ship’s hull with up to 643 pounds of high explosives.
In tests and in theory, this would break the keel of an enemy ship, ripping it in half or opening massive holes in the hull, quickly sending it to the deep.
American submarine commanders headed out with their boats filled with Mk. 14s. They were supposed to use their deck guns as much as possible, since they carried a limited number of torpedoes and each cost ,000 (about 1,000 in today’s money). But when the tactical situation called for firing a torpedo from stealth, like when facing a destroyer or launching a surprise attack against a convoy, they were supposed to fire a few torpedoes and watch the show.
The Mk. 14 torpedo began its career as a deeply flawed weapon, but a series of changes in 1943 would get it fit to fight.
But submarine commanders quickly began reporting problems with their weapons after Adm. Harold Rainsford Stark ordered unrestricted submarine warfare. The Navy’s Bureau of Ordnance thought the weapons should work 98 percent of the time. Submarine commanders were seeing much different results.
In one extreme case, a submarine commander fired all but one of his 16 torpedoes. Of the 15 shots he took, twelve hit the target and only one exploded. And that explosion was at the wrong time. The Japanese target got away with minimal damage.
In another instance, the USS Seawolf fired four Mk. 14 torpedoes at a Japanese transport with no results. That commander had Mk. 10 torpedoes on board, the World War I weapon the Mk. 14 was replacing. Lt. Cmdr. Frederick B. Warder ordered Mk. 10s into the tubes. The first shot hit the target’s stern and the second sank the enemy ship.
The older Mk. 10 was two for two while the Mk. 14 had failed completely. This wasn’t the Seawolf’s first issue with the Mk. 14, either. It had six previous tours under its belt, all plagued by torpedo issues, including that time it fired eight Mk. 14s, which accounted for seven misses and a dud hit.
Some Japanese vessels even reportedly pulled into their ports with Mk. 14 torpedoes sticking out of the hull. They had suffered direct hits, but the warheads had failed to detonate.
The USS Tullibee was destroyed when it fired a torpedo at a Japanese ship in World War II only for it to swim in a circle and hit the submarines instead of the enemy in March, 1944.
Worse, the Mk. 14s had a pesky habit of detonating properly when they circle ran, the worst possible situation. A circle run occurs when a torpedo follows a curved instead of straight path. And uneven drag, propulsion, or warping of a torpedo can cause a circle run and, like the name implies, it sends the torpedo in a circle, back to its starting point.
The Bureau of Ordnance dragged their feet about assessing the problem, and then it took a while to get definitive solutions. So, for two years, submarines went on patrols with faulty weapons that could swim right under the target, pierce it without detonating, or even sink their own submarine.
But the Navy did eventually find the causes of the faults. The circle runs were caused by faulty gyros that failed to straighten the path. The torpedo sometimes swam right under the target because the torpedoes had been tested with faulty depth-measuring equipment and with warheads that didn’t reflect their real buoyancy. The failures to detonate were caused by faulty magnetic and mechanical initiators.
In fact, the mechanical initiator was an especially galling failure as far as submarine commanders were concerned, because they had been told for years that the real problem was them firing from bad angles while a 90-degree hit was most effective. In reality, the mechanical failures were most common at exactly 90 degrees, failing 70 percent of the time in later lab tests.
The Mk. 14 had been in the fleet for nearly 20 years by this point, so it might seem impossible that these faults hadn’t been discovered earlier. But it had been developed during the Great Depression when budget constraints severely constricted the tests and experiments scientists and engineers could do.
Changes were eventually made. The torpedoes were re-calibrated for the proper depth and the magnetic initiators were thrown out entirely. The mechanical ones were faulty thanks to heavy firing pins that couldn’t achieve the right momentum when the torpedo was at full speed, so they were replaced with a lighter metal alloy.
Ironically, the alloy chosen had made it into U.S. arsenals after it was discovered in a Japanese fighter shot down at Pearl Harbor. It fixed the Mk. 14’s mechanical initiation problems, allowing likely detonations no matter the torpedo’s angle of attack.
These changes took the Mk. 14 from one of the worst weapons of World War II to a top contender. It served until 1980, deep into the Cold War.