Japanese Type 97 Torpedo Gyroscope in Case
notes: label: Description
content: This Japanese Type 97 torpedo gyroscope was recovered by members of a U.S. Navy salvage party from the remains of the Imperial Japanese midget submarine I-22tou.
label: Description
content: As part of Japan’s ambitious operation to attack military targets in an around Pearl Harbor, Operation Shinki No. 1 (Divine Turtle Operation No. 1) would covertly send five modified Type A midget submarines into the harbor on the morning of 7 December to launch attacks between the two air attack waves on vessels of the U.S. Pacific Fleet. Two men operated the Type A midget submarine which measured 78 feet in length while armed with two Type 97 17.7-inch, diameter, 220-inch long torpedoes. With a 772 pound explosive warhead, the Type 97 would theoretically give the midget submarines formidable punch.
label: Description
content: Lieutenant Iwasa Naoji, senior most of the officers, led the five midgets into battle. For those midgets that survived the attacks, they would attempt to exit the harbor and rendezvous with the mother submarines off Lanai Island. His Type A midget submarine, I-22tou, launched from its mother submarine, the Type C1 submarine I-22, just after midnight on 7 December approximately nine miles from the entrance to Pearl Harbor. Joining Iwasa in the cramped confines of his boat was Petty Officer First Class Sasaki Naokichi.
label: Description
content: At 7:55AM the first wave of Japanese carrier aircraft began strikes on Oahu. By 8:30AM, destroyer minesweeper Zane (DMS-14) reported sighting an enemy submarine 200 yards astern the repair ship Medusa (AR-1) then anchored at the entrance of Middle Loch to the west of Ford Island. This report reached Lieutenant Commander William P. Buford, commanding the destroyer Monaghan (DD-354). Minutes after Zane’s report, the minesweeper Breese (DM-18) and seaplane tender Curtiss (AV-4) opened fire on a sighted submarine periscope at 8:36AM. A minute later, Monaghan also sighted the submarine’s conning tower and Buford ordered flank speed intent to ram the enemy boat. The midget submarine, I-22tou, fired one torpedo at Curtiss which missed and struck a dock at Pearl City. Curtiss in turn put two five-inch shells through the conning tower of the submarine at 8:40AM, decapitating Iwasa as he likely aimed through the periscope.
label: Description
content: With Monaghan steaming toward the submarine, either Naokichi or Iwasa in his final breath turned their boat toward the American destroyer and fired. The last torpedo passed within 50 yards of Monaghan’s starboard before hitting Fort Island. Within seconds Monaghan struck a glancing blow on I-22tou’s at 8:43AM and dropped two depth charges. The massive explosion blew the submarine back to the surface before it settled 30 feet below. The explosion lifted Monaghan’s stern out of the water and the destroyer lost control before hitting a derrick barge.
label: Description
content: On 21 December, a naval salvage party raised I-22tou’s smashed remains from the bottom of the harbor with a crane and barge. The mangled remains of Iwasa and Naokichi remained entombed in the boat with its bow section completely blown apart. Records remain unclear as to whether the bodies were recovered from the boat. What is known is that the boat became fill for an expansion of the S-1 submarine dock and remains buried beneath a parking lot. Sailors recovered a shredded sleeve with Iwasa’s rank insignia from the boat which the Navy returned to his family in Japan. This insignia is today in the collections of the Yasukuni Shrine.
label: Description
content: Some point after recovery, salvage personnel removed items inside I-22tou. Among these was a small wooden box marked on the lid “Box for Gyro Stabilizer.” Inside the box was a spare Type 97 torpedo gyroscope and assorted small parts for maintaining the device. Personnel gave the cased gyroscope to Rear Admiral William R. Furlong, who found himself after the attack commanding the Pearl Harbor Navy Yard and overseeing salvaging and repair of those ships damaged or sunk during the attack.
label: Location
content: Currently not on view
place: label: associated place
content: Japan
topic: label: related event
content: Pearl Harbor, Attack on
setName: label: See more items in
content: Military and Society: Armed Forces History, Naval
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: AF.58663-N
label: catalog number
content: 58663-N
label: accession number
content: 234065
objectType: label: Object Name
content: Gyroscope
physicalDescription: label: Measurements
content: overall (case): 9 3/16 in x 7 in x 7 in; 23.33625 cm x 17.78 cm x 17.78 cm
label: Measurements
content: overall (gyro): 5 in x 5 1/2 in x 6 in; 12.7 cm x 13.97 cm x 15.24 cm