The first modern frogmen were the Italian commando frogmen, of Decima Flottiglia MAS which was first in action in 1940. They were nicknamed Uomini Rana, Italian for frogmen, because of their swimming frog kick style and because their fins looked like frogs' feet. Their success against Royal Navy warships was a shock to the British Admiralty which took up the challenge and by 1942 the Royal Navy had their own frogmen with manned torpedo Chariots. Many of the early frogmen's breathing sets were German pilots' oxygen cylinders recovered from shot-down Luftwaffe planes. Royal Navy frogmen began with the torpedo chariots, but later moved to midget submarines known as X-craft. On 20 September 1943 two four-man X-craft set out to attack the Tirpitz in Kåfjord in Norway which was badly damaged by limpet mines. This fascinating and well-written book chronicles the use of frogmen during the Second World War, predominantly describing the Royal Navy operatives. It details their training, their various attacks, and the use of frogmen to clear the D-Day beaches of underwater obstacles, and the clearance of mines, booby traps and wrecks in harbors. By the end of the war, the British human torpedo operations had earned their participants 20 medals and 16 men had been killed.