The Japanese Sixth Fleet (Submarines) took part in the Hawaii Operation independently of the First Air Fleet. Of the 25 boats in the fleet, five carried midget submarines. These carriers were all of the I-15 Class, which numbered from 15 to 24. Here the small boats are identified by the addition of the letter A to the number of their carrier. The midget submarines, all of 1939 construction, displaced 46 tons, were some 79 feet in length and a little under 7 feet in diameter. From keel to conning tower they were some 20 feet high.They had two 18-inch torpedo tubes, but no other armament other than the pistol and sword each crewman carried. Their range was about 100 miles at 4 knots, but they could put in a burst of speed of about 24 knots. They had a two man crew. On 7 December they were intended to make their way into Pearl Harbor where their two torpedoes could do fearful damage. Although plans for their recovery after the attack existed, there was, in reality, little hope of their realization and at best the crews expected to get ashore and sell their lives as dearly as possible. The midget submarines were disposed in two arcs centerd on the harbor entrance, I-16A(Ensign Masaharu Yokoyama and PO 2/c Tei Uyeda) on the west and I-20A (Ensign Akira Hiroo and PO 2/c Yoshio Katayama) on the east at the harbor entrance, and outside them from west to east, I-24A (Ensgign Kazuo Sakamaki and PO 2/c Kiyoshi Inagaki), I-22A (Lieutenant Naoji Iwasa and PO 2/c Naojichi Sasaki) and I-18A (Ensign Shigemi Furuno and PO 2/c Shigenori Yokoyama). Between 0100 and 0333 on 7 December the midget subs were released from their mother boats. At 0342 Ensign R. C. McCloy (McCloy, R.C), of Condor, observed what he took to be a periscope wake, but a search failed to confirm the sighting and no report was made. It could have been I-16A. At 0645 Ward shelled and sank a submarine outside the entrance to the harbor and the report of this incident led to Monaghan being ordered to sea. At 0817 Helm sighted a submarine in the harbor entrance and opened fire. At the same time Sakamaki's (Sakamaki, Kazuo) I-24A hit Tripod Reef and he was knocked unconscious. Zane saw another submarine astern of Medusa and Curtiss was already firing. A torpedo was seen explosing harmlessly near the Deperming Station. Curtiss had to cease fire when Monaghan attempted to ram. The submarine was sunk and, when raised a few days later, was found to have been hit with a 5-inch shell which decapitated the commander. At 1004 the light cruiser St Louis was the target for two torpedoes as she passed through the entrance channel. She avoided the weapons and fired on the conning tower of a submarine, apparently successfully. At 1108 Breese followed a motor torpedo boat to the location of a sighting and dropped depth charges. She searched on and at 1133 got a sonar contact and depth charged, throwing up debris and oil. During the afternoon there were numerous reports of submarine sightings, fire being opened and depth charges dropped, but with no sure result. At 2241 the mother submarine I-16 received a message from Yokayama of I-16A: "Successful surprise attack." This led to Japanese claims of a great deal of the damage having been inflicted by submarines, which was not the case. After midnight Breese saw two torpedoes coming for her, but avoided them. They might have been from I-16A, but at 0111 contact with that boat could not be established. Sakamaki in I-24A was stuck on a reef, got off and ran aground once more to become the only survivor and only prisoner of the entire enterprise; and the first prisoner of the war.