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. These were part of the ''1ª Flottiglia Mezzi d'Assalto
(MAS), the "First Assault Vehicle Flotilla" (later called Decima Flottiglia MAS), an elite naval sabotage unit of the Royal Italian Navy (Regia Marina Italiana''). As commander of
Sciré Borghese took part in several raids using SLC. The first of these, in September and October 1940,
were directed at Gibraltar. The September raid was abandoned when the harbour was found to be empty. In the October raid, Borghese took
Sciré deep into
Gibraltar Bay, making a difficult submerged passage in order to release the SLC as close to the target as possible. For this he received the
Medaglia d'Oro al Valor Militare (MOVM), despite the mission's overall lack of success. In May 1941 a further attempt ended in failure, but on 20 September 1941, a successful mission damaged three merchant ships in the harbour. After this last attack, he was promoted to
Capitano di Fregata, and named commander of the
Decima MAS' sub-surface unit. On 18 December 1941, he reached
Alexandria in
Sciré and launched
the daring raid by three SLCs that heavily damaged the two
Royal Navy battleships and and two other ships in the harbour. The six Italian Navy crew that attacked
Alexandria harbour all received the ''Medaglia d'Oro al Valor Militare
, and Borghese was named Cavaliere dell'Ordine Militare di Savoia''. In May 1943, Borghese took command of the
Decima Flottiglia MAS ("10th Assault Vehicle Flotilla"), or
Xª MAS with
Roman numerals, which continued active service in the Mediterranean and pioneered new techniques of
commando assault warfare. The Roman numeral was in memory of Caesar's famous Decima Legio.
8 September 1943: the Armistice After
Italy's surrender to the Allies on 8 September 1943, the
Xª MAS was disbanded. While some of its sailors joined the Allies, Borghese chose to continue fighting with the
Italian Social Republic (RSI) alongside the German Armed Forces (
Wehrmacht). On 12 September 1943, he signed a treaty of alliance with Nazi Germany's
Kriegsmarine. Many of his colleagues volunteered to serve with him, and the Decima Flottiglia was revived, headquartered in
Caserma del Muggiano,
La Spezia. By the end of the war, it had over 18,000 members, and Borghese conceived it as a purely military unit. The X Flottiglia gained a reputation for never firing a shot at any Italian military units fighting with the Allied forces. In April 1945 when the
US command discovered that the British had granted permission to Marshal
Josip Broz Tito of
Yugoslavia, and his Communist troops, to occupy northeastern Italy from Venice to the east, Borghese moved the bulk of the X Flottiglia from the Ligurian and Piedmontese area to the Veneto. The X Flottiglia built a line of defence on the Tagliamento river where they resisted until the arrival of the Allied troops. In this action, the X Flottiglia lost over eighty per cent of the fighting sailors dispatched to the front against Tito's troops, and the Italian Communist Partisans allied with Tito. At the end of the war, Borghese was rescued by
Office of Strategic Services officer
James Angleton, who dressed him in an American uniform and drove him from
Milan to
Rome for interrogation by the Allies. Borghese was then tried and convicted of collaboration with the Nazi invaders, but not of
war crimes, by the Italian Court. He was "sentenced to 12 years imprisonment, discounted to 3 years, due to his glorious expeditions during the war, his defence of northeast borders against Tito's
IX Corps and his defence of
Genoa harbour". He was released from jail after four years' imprisonment by the
Supreme Court of Cassation in 1949. ==Political activism after the war==