On 22 August 1940, in the Gulf of Bomba, the Italian submarine Iride, being a human torpedo carrier, was sunk by a torpedo released by a BritishFairey Swordfish bomber. The air attack happened during an exercise, in shallow water, when four human torpedo squads were around, including officers Teseo Tesei and Luigi Durand de la Penne. The divers were able to make an immediate rescue action. Of the 12 Iride crewmen who survived, two died during an unsuccessful attempt to surface, nine were retrieved alive, and one was too shocked to leave the sunken submarine. De la Penne tried to persuade him to surface, and even gave him his own aqualung, but the seaman refused surfacing and died.
Sinking of ''Valiant''
As part of a team of divers he took part in the human torpedo attacks on British vessels in the Mediterranean. In December 1941, he was one of a team of six that attacked Alexandria harbour. They used an Italian human torpedo known as S.L.C., actually a small underwater assault vehicle with a crew of two. As a result, four ships were disabled: the British battleships and , and the oil tanker Sagona and the destroyer. De la Penne personally placed the limpet mine under the hull of Valiant. SLC or "Maiale", exhibited in the Museo Sacrario delle Bandiere delle Forze Armate, in Rome, Italy. Of the three teams of frogmen, only de la Penne and Bianchi were captured before the devices exploded. The other two teams were able to get the coast, but they were captured the day after in Alexandria. As de la Penne refused to inform the ship's captain of the mines, he and his mate were confined in a cell under-deck, actually in a place just above where the mine had been placed. A few minutes before the detonation, De la Penne informed Captain Morgan of the imminent explosion, in order to allow the British to evacuate the ship, but continued to refuse to disclose where the mine had been placed. The two frogmen were immediately sent back to their confinement place. Few minutes later, the mine exploded. Although hurt by the explosion, the frogmen reached the deck of Valiant just in time to see the other mines explode under Queen Elizabeth, Sagona and Jervis. Although both ships settled on the sea bed, their decks were still clear of the waterline. As all six frogmen were eventually captured and both vessels appeared to be operational, the success of the attack in neutralising the British ships became known by the Italian Navy only after some days. For this action, de la Penne was awarded the Gold Medal of Military Valour, the Italian highest military decoration awarded for valour "in the face of the enemy". In May 1945, at the end of the war, the then Admiral Charles Morgan – who was Valiants captain at the time of the attack in Alexandria – wanted to confer himself the medal to de la Penne in a ceremony in Taranto.
After the 8 September 1943Armistice, de la Penne was offered the opportunity to be released from prison and fight for the Allies. He accepted and returned to duty as a frogman. On 22 June 1944, he participated in a joint Italian/British operation against the Germans. A team formed of British and Italian divers was transported by the Italian destroyer in an attack on La Spezia harbour, at the time in German hands. They sank the cruisers and before they could be used to block the harbour entrance.
Post-war career
After the war, Durand de la Penne stayed in the Marina Militare. He was promoted to Capitano di Fregata in 1950 and Capitano di Vascello in 1954. In 1956 he was appointed as naval attaché in Brazil. He was also Deputy of the Parliament of Italy for the second through the sixth legislatures as an independent candidate. He retired with the rank of Ammiraglio di Squadra. In the 1962 filmThe Valiant he was played by Ettore Manni. In his honour, the Marina Militare named its new series of destroyers of 1993 as the. Two vessels were launched: the lead ship, Luigi Durand de la Penne and Francesco Mimbelli.
