It is, perhaps, not generally realised that swimmer delivery vehicles (SDVs) have been in existence for almost 100 years; nor is it always understood that SDVs themselves have to be delivered, and that they need not necessarily be submersible. Canoes, for example, have often been carried by submarine, surface ship or flying boat to a drop-off point before conveying frogmen armed with limpet mines on their final, underwater approach to a target. Many modern SDVs too are transported by larger submarines.Proposals for a 'human torpedo' - indeed for a midget submarine - were first mooted in 1909 by a retired British naval commander, and by 1911 an early type of breathing set was being developed in Germany. During the First World War, the Italian Navy developed a manned vessel - a modified torpedo using compressed air as the propulsion system -that could carry an explosive charge more than 10 miles at 4 kt. In October 1918, one of these 'human chariots' was used to blow up the Austro-Hungarian battleship Viribus Uni-tis at Pula (in what is now Croatia). Italy also extended one of its submarines to house 10 swimmers in an attempt to capture the port. Ideas proliferated during the inter-war years until an underwater attack succeeded on 19 December 1941, when three Italian two-man human torpedoes - transportedby the submarine Scire - were used to place delayed-action charges on the hulls of the British battleships HMS Queen Elizabeth and HMS Valiant, the destroyer HMS Jervis and the tanker Sagona in the supposedly safe harbour of Alexandria, Egypt.
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