At the start of the Second World War, Borghese took command of submarine Vettor Pisani, and in August 1940 was in command of submarine Sciré, which was modified to carry the new secret Italian weapon, the human torpedo. Known as "slow speed torpedoes" (siluri a lenta corsa, or SLC), and nicknamed "pigs" (maiali) for their poor maneuverability, these were small underwater assault vehicles with a crew of two.