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ANTONY PRESTON, JOHN BATCHELOR
In 1925 the British decided to remove the 12-in guns from their two surviving "M" Class submarines, and M2 was converted to carry a seaplane. A large hangar was built forward of the conning tower, with a large crane on its roof; a light inclined catapult was built on the forward casing, and a specially designed Parnall Peto seaplane was carried. The biggest problem of handling an aircraft on board a submarine was the lack of space, and this dictated very small machines, which in turn lacked the capacity for fuel which would have made them more useful.
Sopwith Baby. With its 25 ft 8 in wingspan and maximum speed of 100 mph, the Sopwith Baby was successfully flown off a British submarine in 1916. Performance and range were too limited to produce any positive results, however, as was the case with similar experiments with German U-Boats
Then, in 1932, the Japanese launched their prototype 15. They stowed the fuselage and floats in one hangar and the wings in another, sited to port and starboard under the conning tower. The time taken to assemble the seaplane was so long that the submarine would almost certainly have been sunk in the middle of the operation. The 16 had the same problem, but she did at least have a catapult like the M2. Thereafter a seaplane and catapult became a feature of the larger types of Japanese submarines, and special tactics were devised to exploit the combination.
In 1916 the Norwegian Navy bought Farman floatplanes for trials, and when they broke down or ran out of fuel submarines were able to recover them by surfacing gently underneath. In this photograph a recovered seaplane is being lifted off the casing of submarine A4. Note the spare float lashed to the submarine's casing
The sister of M2 was converted to a minelayer at the same time, as a development of the U71 type. M3 had a free-flooding casing (i.e. outside the pressure hull) containing twin mine-tracks, which ran from well forward past the conning tower. She was a great success, although ungainly in appearance, and she was followed by a class of six more. The main innovation in the M3 was the provision of powered chain conveyor gear, which allowed the use of a normal mine and sinker, rather than the special type of mine which had to be used in all First World War minelayers.
The Washington Disarmament Conference of 1921/22 and the Treaty which resulted were the outcome of the rivalry which had grown up between the United States and Japan during the First World War. Although the Treaty is best known for its limitations on large surface warships, it also dealt with submarines. The British delegation was not unnaturally content to see the submarine banned, but this was a futile quest so soon after the great submarine campaign of 1915-18. The Italians and French were particularly anxious to retain a large fleet of submarines as a cheap alternative to new battleships and aircraft carriers, and the Japanese made little secret of their intentions to build up a big fleet to threaten American superiority in the Pacific. Lord St Vincent's words of 1801 had come true, and neither of the two largest navies really wanted to see any progress made with the weapon most likely to destroy their own superiority.
Stored German Arado 231
The best that could be done was to limit the gun-calibre to 8 in, as in heavy cruisers, but the French were particularly obdurate in rejecting limitations on numbers of submarines and in blocking attempts to outlaw unrestricted warfare. The world's major navies, denied the opportunity of building unlimited numbers of surface warships as much by economics as by international agreement, plunged into an orgy of submarine building.
The smaller navies were also conscious of the value of submarines, and the Nether-lands and the Scandinavian countries had developed their own designs with some success. The Royal Swedish Navy had been building submarines since 1908, but the first fully indigenous design, the Sjölejonet Class, was not ordered until 1934. They displaced 580 tons on the surface, were 210 ft in length, and had a submerged speed of 9 knots. The disposition of torpedo tubes was unusual - three 53-cm (21-in) bow tubes, two rotating deck tubes similar to those on French boats, and a single stern tube; two single 40-mm deck guns were carried in retractable mountings, an idea derived from Dutch submarines. Three were completed in 1938/9, and a further six were ordered when the international situation worsened.
Martin Kitten. The Martin Kitten was the first aircraft specially designed for operating from submarines. 4 were ordered in 1922 but only one prototype survives. It is unusual in having wingtip ailerons and also in having wheels instead of floats. This meant that the aircraft had to do a crash-landing after completing its mission, but the cockpit is so cramped that the pilot would have extreme difficulty in baling out. In fact, pilots would probably have been chosen for their lack of stature and expendability if it had gone into service
Denmark lacked the resources of Sweden, but she too produced original designs like the "H" Class, whereas Norway was more content to rely on foreign designs. The "B" Class were completed in the early 1920s to an American Electric Boat Company design of 1914 vintage, but B1 nevertheless served in the Second World War. Poland had a small force of five boats, comprising the Dutch-built Sep and Orzel and a trio of French-built 980-tonners, the Rys, Wilk and Zbik, of which the Orzel and Wilk managed to escape to Britain in September 1939 in a desperate dash for freedom.