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ANTONY PRESTON, JOHN BATCHELOR
American 5-in Submarine Gun. The 5-in/25 cal. Mk XIII gun shown was mounted on board USS Tigrone (SS419), one of the few Tench Class to be completed before the end of the war. Many weapons were carried by US submarines, but this pattern was the most popular. Weight: 21 tons. Range: 14,500 yards at 40° elevation. Weight of shell: 53 lb
Japanese submarines were well aware of the need to attack American shipping, but failed to get a hearing from their superiors. When things began to go badly in 1942 the response was to hurl submarines into useless attacks on landing forces, or to use them to transport supplies to isolated Army garrisons. Not satisfied with this, the Army began to build transport submarines of its own, surely the most monumental dispersion of effort in the history of naval warfare; about 28 were built, and they were manned by Army personnel. When permission was given to attack communications it was too late, and in any case reliance was placed on the Kaiten, which were hardly suitable for extended operations. Like the Italian "pigs" the Kaiten were transported on the decks of submarines, and were launched when close to the operational area.
Japanese I70. The lack of numerical sequence makes Japanese submarine classes hard to follow; 170's sisters were renumbered I168-169 and I171-172. They were big ocean-going submarines with a range of 14,000 miles on the surface. I70 was sunk by carrier aircraft only three days after the attack on Pearl Harbor. Displacement: 1,785 tons (surfaced). Armament: Six 21-in torpedo-tubes; 14 torpedoes carried; one 3·9-in AA gun; one 13-mm machine-gun. Speed: 23 knots (surfaced), 8¼ knots (submerged)
The last flowering of Japanese submarine design was typically ambitious. In 1942 they ordered 17 of the Type STo, the largest submarines ever seen up to that time. These were the famous 1400 Class, an amalgamation of the Type A, B and C submarines, to produce an aircraft-carrying boat which could attack the Panama Canal. For this purpose they were meant to carry two seaplane bombers, but were altered to carry three in the hangar. In layout they followed the previous big submarines, but to keep the draught down as much as possible a peculiar double cylindrical hull was tried, with the cylinders side-by-side. The armament was heavy, eight 21-in bow torpedo-tubes with 20 reloads, and four torpedoes and 15 bombs carried for the seaplanes.
Only three of these giants were completed by August 1945, when Japan capitulated. When American technical experts examined them they found a lot of evidence of technical assistance from the Germans. Many German U-Boats had made trips out to the Far East to collect cargoes of rubber, tin and wolfram, and the Japanese had been very anxious to copy the features which made these boats so superior to their own. The 1400 Class had a schnorchel, and, even had the same rubber coating on the hull which was being tried out in Germany as a means of absorbing Asdic pulses.
Japanese I402. The I400 Class were ordered under the modified 1942 programme and were the I largest submarines built up to that time. The intention was to provide them with three seaplane bombers in order to attack the Panama Canal, but the aircraft never reached production. Only three boats were completed by August 1945, and they were surrendered to the American occupying forces. Displacement: 5,223 tons (surfaced). Armament: Eight 21-in torpedo-tubes; 20 torpedoes carried; one 5·5-in gun; ten 25-mm AA guns
It would not be correct to suggest that the Japanese submarine effort was only directed towards large submarines, because in one way they anticipated the Germans in developing a boat with high underwater speed. In 1937/38 they built No.71 in conditions of utmost secrecy, even to the point of launching her behind a smokescreen. She was small, only 140 ft long and displacing 213 tons on the surface, but she reached 21 knots under water. Although she never entered service, being nothing more than an experimental boat, she revived the ideas which had been tested and forgotten with the British "R" Class twenty years earlier. During the war two operational classes were built to develop her ideas, the small Ha201 Class and the larger I201s.
Despite these interesting developments the Japanese submarine effort during the Second World War was a costly failure. Losses were extremely heavy; out of 245 submarines which served in the war (excluding ex-German and Italian boats taken over and midgets) 149 were sunk, a loss ratio of 60 per cent. There were few successes to match the exploits of the Germans, largely because the peacetime policy and training had proved totally wrong. The only successes of the aircraft-submarine tactics which the Japanese had developed so diligently came in 1942; a scout plane reconnoitred Diego Suarez harbour before a midget was sent in to torpedo a British battleship and another tried to set the Oregon pine forests alight with incendiary bombs. Otherwise this costly programme was entirely wasted.