Pearl Harbor Attack Mysterious Fifth Midget Sub
Type A Kō-hyōteki, NO. 16 During Pearl Harbor

The remains of a Japanese mini-submarine that participated in the Dec. 7, 1941, attack on Pearl Harbor have been discovered, researchers are to report today, offering strong evidence that the sub fired its torpedoes at Battleship Row.

That could settle a long-standing argument among historians.

Five mini-subs were to participate in the strike, but four were scuttled, destroyed or run aground without being a factor in the attack. The fate of the fifth has remained a mystery. But a variety of new evidence suggests that the fifth fired its two 800-pound torpedoes, most likely at the battleships West Virginia and Oklahoma, capsizing the latter. A day later, researchers think, the mini-sub's crew scuttled it in nearby West Loch.

The loch was also the site of a 1944 disaster in which six tank landing ships preparing for the secret invasion of Saipan were destroyed in an ammunition explosion that killed 200 sailors and wounded hundreds more.

When the Navy scooped up the remains of the so-called LSTs and dumped them outside the harbor to protect the secrecy of the invasion, it apparently also dumped the mini-sub's remains, which were mingled with the damaged U.S. ships.

The remains of a Japanese mini-submarine that participated in the Dec. 7, 1941, attack on Pearl Harbor have been discovered, researchers are to report today, offering strong evidence that the sub fired its torpedoes at Battleship Row.

That could settle a long-standing argument among historians.

Five mini-subs were to participate in the strike, but four were scuttled, destroyed or run aground without being a factor in the attack. The fate of the fifth has remained a mystery. But a variety of new evidence suggests that the fifth fired its two 800-pound torpedoes, most likely at the battleships West Virginia and Oklahoma, capsizing the latter. A day later, researchers think, the mini-sub's crew scuttled it in nearby West Loch.

The loch was also the site of a 1944 disaster in which six tank landing ships preparing for the secret invasion of Saipan were destroyed in an ammunition explosion that killed 200 sailors and wounded hundreds more.

When the Navy scooped up the remains of the so-called LSTs and dumped them outside the harbor to protect the secrecy of the invasion, it apparently also dumped the mini-sub's remains, which were mingled with the damaged U.S. ships.

No torpedoes were found on the wreck, and evidence suggests that they were not present when the boat was sunk. A newly declassified photograph taken by a Japanese plane during the attack appeared to show a mini-sub firing a torpedo into Battleship Row. A report to Congress in 1942 by Adm. Chester W. Nimitz describes an unexploded 800-pound torpedo recovered after the battle. That's twice the size carried by the torpedo bombers.

That torpedo was apparently a dud that missed the West Virginia.

But an examination of the remains of the Oklahoma shows that it apparently had underwater damage much larger than that associated with aerial torpedoes. An underwater blast would have caused it to capsize, Stephenson said. "Otherwise it would have settled to the bottom upright," like the other sunken ships.

The 1944 disaster at West Loch occurred on May 21 as the Navy was preparing to invade the Mariana Islands in Operation Forager. The Navy clamped a top-secret classification on the incident to keep it from the Japanese, and few records are now available. What is known is that it was crucial to clear out the debris because the loch was by then the site of an ammunition dump.

Records from the salvage ship Valve showed that it was brought into the loch during the cleanup and its 250-ton crane was used for an undisclosed reason. Stephenson thinks it lifted the I-16-tou, but there are no records to confirm that.

The remains of the mini-sub were then dumped three miles south of Pearl Harbor along with those of the LSTs, to be found by Kerby 50 years later.

Bulkheads on the wreck are sealed, so researchers don't know whether the mini-sub crew was trapped. But a map taken from one of the other mini-subs showed the location of a safe house in Pearl City, Hawaii, suggesting the crew might have scuttled the boat and escaped.

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In 2009, a research team assembled by PBS Nova positively identified the remains of a midget sub found outside the Pearl Harbor entrance as being the last, No.16, of the 5 Ko-Hyoteki that participated in the December 7, 1941, attack. It was discovered in salvage from the wreckage of the West Loch Disaster of 1944, dumped three miles south of Pearl Harbor. Secret war records show that submarine crews had been ordered to scuttle their subs after the attack and provisions were made to recover stranded crews. It is believed by some that the fifth sub successfully entered Pearl, fired on Battleship Row
(still controversial), and escaped to the relative quiet of neighboring West Loch, where it was scuttled by the crew. When a series of explosions sank an amphibious fleet being assembled in the Loch in 1944, the remains of the sub were collected and dumped in the subsequent salvage operation, which was kept classified as secret until 1960. The torpedo tubes in the bow section were empty, indicating that the fifth midget may have fired its torpedoes prior to being scuttled. A photograph taken from a Japanese plane during the Pearl Harbor attack shows what might have been a midget submarine inside the harbor firing torpedoes at Battleship Row. The capsizing of the USS Oklahoma may have been accelerated by a torpedo hit from a submarine-launched torpedo, the warheads of which were larger than the aerial torpedoes. Some believe that in the photo, where the torpedoes' paths had supposedly started, were sprays that indicated a midget-submarine rocking up and down due to the force of the torpedo being launched, causing the propellers of the stern to be exposed, kicking up clouds of water spray. A war time report from Admiral Nimitz confirmed the recovery of at least one dud torpedo of the type employed by the midget submarines. This discovery is covered in PBS Nova television program Killer Subs in Pearl Harbor and companion website, I-16tou.com.