As ships, vehicles boats b and C were used landing ships of type T-1.
In December 1943 on the basis of the submarine-type started designing larger boats of type D (or Cogui). The main differences from the submarines of the type consisted in the installation of more powerful diesel-generator – with him the charging process of the battery fell to eight hours, increased the seaworthiness and improved the conditions of habitability of crew increased to five people. In addition, the body has become noticeably stronger, which increased the depth of the dive up to 100 M.
In the spring of 1945, before the end of the test, the lead ship, was deployed for the serial construction of submarines. In accordance with the plans of the naval command, in September 1945, was supposed to deliver the fleet of 570 units with the subsequent pace of construction -180 units per month. To speed was applied sectional method (boat was assembled from five sections) that reduce construction period up to 2 months. However, despite involvement in the construction of Koryu large number of shipyards, the rate of delivery to the fleet of these submarines could not be fully maintained, and by August 1945, in the ranks there were only 115 boats, and 496 were at different stages of construction.
On the basis of the midget submarine (SMPL) Koryu in 1944, a project was developed midget submarine mine-layers M-Kanamono (the literal translation is “Metal product Type M”), is intended for the production of the mine jars in places of basing of the enemy. Instead of torpedoes he was carrying mine tube containing four bottom mines. Managed to build only one submarine.
The performance characteristics of the Japanese midget submarines
At the end of the war, apart from the family of dwarf submarines, leading descended from the submarines of type A (types A, b, C and D), the Japanese fleet was replenished as submarines of the smaller type Kairyu (their characteristic feature was the fixed side rudders (fins) in the middle of the hull. Design armament consisted of two torpedoes, but the lack of them has led to the emergence of a variant of the boat with a 600-kg explosive charge instead of a torpedo, effectively turning them into human torpedoes.
Serial construction of submarines of the type Kairyu began in February 1945. To accelerate the works it was conducted by the sectional (sub divided into three sections). Plans of the marine leadership was provided by September, 1945, to put the fleet 760 ultra-small boats of this type, but by August it was commissioned only 213 units, and 207 were under construction.
Information about the fate of the Japanese midget submarines is sketchy and often contradictory. It is known that during the attack on pearl Harbor on 7 December 1941 was lost 5 midget submarines of the type A.
Young submarine officer aggressively sought the inclusion of a midget submarine operations against pearl Harbor. Finally, in October the command was allowed to include them, with the condition that the drivers will return after the attack. Work started. Kure first arrived I-22 for inclusion in the design of the necessary improvements.
Several days later another three arrived. The fourth submarine, I-24, just built in Sasebo and immediately began her sea trials.
Submarines arrived commanders: Lieutenant Iwasa Naoji (I-22), sublieutenant Yokoyama Isamu, Masaharu (I-16), sublieutenant Haruno Shigemi (I-18), second Lieutenant, Hiroo Akira (1-20) and Lieutenant Sakamaki Kazuo (I-24). The second crew was a non-commissioned officers: Sasaki Naoharu (I-22), Ueda Tazi (I-16), Yokoyama Isamu, Harunari (I-18), Katayama Yoshio (I-20), Inagaki, Kyoji (I-24). Characteristic detail: the crew was formed only from unmarried divers, from large families, and not eldest sons. Sakamaki Kazuo, for example, was the second of eight sons.
The connection of the midget submarines was called “Tokubetsu Kogekitay”, abbreviated as “Tocco”. This phrase can be translated as “a Compound special attack” or “Special marine drum connection”.
Early on the morning of November 18 submarines left Kure, stopping briefly at Oradaki to pick up small boats. In the evening they headed for pearl Harbor. Boats walked 20 miles from each other. Flagman – I-22-was in the center. In the daytime the boat was under the water for fear of detection, and surfaced only at night. According to the plan they were supposed to arrive at the collection point located 100 miles South of pearl Harbor, at night, after sunset, two days prior to the attack. Once again checking the boat under the cover of darkness, the sub-carriers were then to go to pearl Harbor, to take a position within 5 – 10 miles from the entrance to the harbour and disperse the arc. Three hours before dawn the first shall launch their midget boats left the submarine I-16. Then successively, at intervals of 30 minutes start super small boats with native speakers I-24, I-22, I-18. And finally, the dwarf boat with the last boat I-20 had to go through a shot of the harbour half an hour before sunrise. In the Harbor all boats were ordered to lie on the bottom, and then join the aerial attack and inflict maximum destruction for its ten torpedoes.
3:00 super small boats launched, and the boat-carriers started to dive. No luck “little one” Lieutenant Sakamaki. Failed gyrocompass repair failed. It was already 5:30 and she still wasn’t ready to go, being late for two hours from set up time. Dawn was approaching, when Sakamaki and Inagaki squeezed into the hatch of his boat.
The entrance to the Bay of pearl Harbor was blocked by two rows of anti-submarine nets. American trawlers each morning spent trawling the control of the waters surrounding the base. Slip them into the Bay was easy. However, the plans of the Japanese were violated from the very beginning. 3:42 minesweeper Condor detected the periscope of a submarine in front of the entrance to the Bay. In her search included the old destroyer “ward” was built in 1918. Around 5:00 PM the Americans opened a passage in the networks to skip the trawlers, and transport, tug and barge. Apparently, two midget submarines managed to secretly penetrate into the harbour, and the third was seen with a “ward” and circling over the sea flying boat “Catalina”.
Above the surface of the water stood the cabin of the boat and part of the cigar-shaped hull. It seemed that she didn’t notice, moving in the harbour at a speed of 8 knots. “Ward” opened gun fire to direct fire from a distance of 50 meters and from the second shot hit the base of the cuttings. The boat shuddered, but continued the movement with a ragged hole in the cockpit. Four explosions of depth charges ripped the boat in half. His contribution made and “Catalina”, and dropping a few bombs. Allegedly came under attack boat Lieutenant IVaS boat carrier I-22.
Lieutenant Sakamaki and petty officer Inagaki more than an hour desperately trying to correct the trim of your boat. With difficulty they managed to do it, and they reached the entrance to the Bay. The gyrocompass was still faulty. Sakamaki was forced to raise the periscope, and noticed a boat from the destroyer “helm”. Immerse yourself and walk away from him, the boat hit a reef and popped out of the water. The destroyer opened fire and rushed to the RAM. However, he rushed past, while the boat managed to break free from the reef and leave, but as a result of hitting the reef one torpedo stuck in the hull began to enter the water. Due to the chemical reaction of water with sulfuric acid of the batteries, which was released suffocating gas. Somewhere at 14:00 the submarine again came to the reef. Out of order the second torpedo.
In the morning of December 8, helpless uncontrollable the boat was close to shore. Sakamaki started the engine, but the boat again came across the reef! This time it stuck firmly. Sakamaki decided to blow up the boat, and to reach land by swimming. Inserting explosive charges, the detonators, he lit the fuse. Sakamaki and Inagaki threw herself into the sea. Was 6h. 40 minutes… Jumped into the water after the commander Inagaki drowned. The weakened Sakamaki on the shore captured five patrolmen 298 th American infantry division…
Damaged aircraft transport Yamazuki Mages and dwarf submarine Type With a cast on the shores of Guadalcanal
Midget boat Koryu Type D at the shipyard of Yokosuka Naval Base, September 1945
In 1961, the Americans picked up the boat (a Type), sunk in December 1941 in the channel of pearl Harbor. The hatches of the boat opened from the inside, several publications reported that the mechanic of the boat during Naoharu escaped and was captured
Restored submarine For-51 (Type C), exposed on GUAM
History of the submarine Lieutenant Sakamaki known in sufficient detail, which is not true of four other submarines. Most likely, only two midget managed to penetrate the harbour. And without any problems entered the harbour only boat Lieutenant Emami. However, she was noticed when she surfaced 700 metres from the seaplane base “Curtiss”. The gunners have made two hits in her, but she managed to launch two torpedoes exploded on the shore. Destroyer “Monaghan” rammed the boat and in addition dropped depth charges.
Another midget submarine, most likely, was sunk at 10:00 cruiser “St. Louis”. Heading to the exit of the Bay, it was exposed to torpedo attack. Evading two torpedoes, the cruiser found the boat for the external side of the network fence, and fired at her. As for the fifth boat, it, that managed to sneak into the Harbor, where he participated in a torpedo attack of the battleship, and then sank together with the crew (may have been sunk by them).
From other operations of the midget submarines should be mentioned that three more boats of this type died 30 may 1942 in the area of Diego-Suarez, and four in Sydney harbour on 31 may 1942.
During the fighting in the Solomon Islands in 1942, killing eight submarines of type A (including Na-8, Na-22 and Na-38). In the Aleutian Islands 1942 – 1943 killed three submarines of type A. In 1944 – 1945 years in the defense of the Philippines and the island of Okinawa killed eight boats type C.
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The Washington naval agreement of 1922 was a significant barrier to growing the race for naval armaments, which began during the First world war. Under this agreement the Japanese fleet by number of aircraft carriers and capital ships (battleships, cruisers) are much smaller than the fleets of England and the United States. Some compensation for this could serve as a permit for the construction of the points of forward basing in the Pacific Islands. And because agreements about the number of submarines to achieve in Washington and failed, the Japanese admirals began to plan the placement on remote island bases of small coastal boats.