The first of the manned torpedoes was the Siluro Lenta Corsa (SLC), `slow speed torpedo’, nicknamed the maiale or `hog’, first developed by Tesei and Toschi in 1935-36. By summer 1939 about 11 of these were available, but it was not until July 1940 that the new generation entered production. These were designated Series 100, and followed in 1941 by the improved Series 200. They were based on the standard 533mm torpedo with suitable adaptations: the double propellers were replaced by a single larger one in an enclosed structure to prevent snagging on nets, and seats for two crewmen and superstructures housing controls were added. The SLC weighed from 1.3 to 1.4 tons, and measured between 6.7 and 7.3m (22-24ft). The 1.6hp electric motor gave a speed of 2-3 knots, to a depth of between 15m and a theoretical maximum of 30m (49-98ft). Once they reached their target the two crewmen had to detach the 1.8m (5.9ft) explosive warhead; this contained a charge of between 230kg and 260kg (507lb-573lb), or, in the last model, two 125kg (275lb) charges. By September 1943 some 50 examples had been built; by then they were largely outdated in comparison with the British `Chariots’ and the new Italian Siluro San Bartolomeo (SSB) – though only three prototypes of this greatly improved model had been built by the time of the Italian surrender.
On 19 December in 1941, limpet mines placed by Italian divers sink the HMS Valiant (1914) and HMS Queen Elizabeth (1913) in Alexandria harbour.
Developed in 1918, by two divers of the Italian Navy-Raffaele Paolucci and Raffaele Rossetti, they rode a primitive manned torpedo into the Austro-Hungarian Naval base at Pola, and sank the Austrian battleship Virbus Unitis and a freighter. Sans breathing gear, they rode in with there heads above water. Both men were discovered and captured, but not before their success.
As a result of this first attempt, the First Fleet Assault Vehicles were formed in 1939, by Major Teseo Tesei & Elios Toschi of the Italian Royal Navy. In 1940, Commander Moccagatta of the IRN, reorganized this group, into the Tenth Light Flotilla of Assault Vehicles aka X-MAS. It constructed manned torpedoes and trained navy frogmen. The IRN X-MAS group attempted an attack on Valletta Harbor in July of 1941, which was a complete disaster and which resulted in the death of Major Tesei.
A better design, was the Italian Human Torpedoes, called Maiale-meaning “Pig,” as it was slow to steer. Three feet high and 23 feet long, it was electrically powered by a 2 hp electric motor. It had a crew of two, which rode atop the device and had a max. speed of 4 knots. It carried a detachable 300 kg warhead.
During the war Italian Special Forces unit Decima MAS (10th Flotilla, aka X-MAS) pioneered various diving and submersible technologies and used them to devastating effect against the Allies. The main underwater vehicle was the SLC (Siluro a Lunga Corsa which means long running torpedo’, and not the common mistake of ‘Siluro a Lenta Corsa’ which means slow running torpedo, and is incorrect). This was described as a ‘human torpedo’ and popularly known as the ‘maiale’ (pig). Two frogmen sat astride a torpedo body with a massive mine carried on the nose. They would creep into an enemy port and attach the mine to the target using clamps. Suspended between the bilge keels, the mine was large enough to sink a capital ship. The SLC was used on several successful attacks on Allied shipping in the Mediterranean including the disabling of two battleships. The effectiveness of these tactics led the British to copy the design, developing the Chariot. Following the SLC, Decima MAS developed the more advanced SSB (Siluro San Bartolomeo) with the crew sitting inside the craft. The SSB never saw combat because it arrived too late, but was the model which influenced the post-war development of SDVs. Pucciarini was himself an SSB pilot.
The Raid on Alexandria was carried out on 19 December 1941 by Italian Navy divers, members of the Decima Flottiglia MAS, who attacked and disabled two Royal Navy battleships in the harbour of Alexandria, Egypt, using manned torpedoes.
On 3 December, the submarine Scirè of the Italian Royal Navy (Regia Marina) left the naval base of La Spezia carrying three manned torpedoes, called maiali (pigs) by the Italians. At the island of Leros in the Aegean Sea, the submarine secretly picked up six crewmen for them: Luigi Durand de la Penne and Emilio Bianchi (maiale nº 221), Vincenzo Martellotta and Mario Marino (maiale nº 222), and Antonio Marceglia and Spartaco Schergat (maiale nº 223).
On 19 December, Scirè—at a depth of 15 m (49 ft)—released the manned torpedoes 1.3 mi (1.1 nmi; 2.1 km) from Alexandria commercial harbour and they entered the naval base when the British opened their defenses to let three of their destroyers pass. There were many difficulties for de la Penne and his crewmate Emilio Bianchi. First, the engine of the torpedo stopped and the two frogmen had to manually push it; then Bianchi had to surface due to problems with the oxygen provider, so that de la Penne had to push the Maiale alone to where HMS Valiant lay. There he successfully placed the limpet mine, just under the hull of the battleship. However, as they both had to surface, and as Bianchi was hurt, they were discovered and captured.
Questioned, both of them kept silent, and they were confined in a compartment aboard Valiant, under the sea level, and coincidentally just over the place where the mine had been placed. Fifteen minutes before the explosion, de la Penne asked to meet with Valiant’s captain Charles Morgan and then told him of the imminent explosion but refused to give further information, so that he was returned to the compartment. Fortunately for the Italians, when the mine exploded just before them, neither he nor Bianchi was severely injured by the blast, while de la Penne only received a minor injury to the head by a ship chain.
Meanwhile, Marceglia and Schergat had attached their device five feet beneath the battleship HMS Queen Elizabeth ‘s keel as scheduled. They successfully left the harbour area at 4:30 am and slipped through Alexandria posing as French sailors. They were captured two days later at Rosetta by the Egyptian police while awaiting rescue by the Scirè and handed over to the British. Martellota and Marino searched in vain for an aircraft carrier purportedly moored at Alexandria, but after sometime, they decided to attack a large tanker, the 7554 gross register ton Norwegian Sagona. Marino fixed the mine under the tanker’s stern at 2:55 am. Both drivers managed to land unmolested but were eventually arrested at an Egyptian checkpoint.
In the end all the divers were made prisoners, but not before their mines exploded, severely damaging both HMS Queen Elizabeth and HMS Valiant, disabling them for nine months and six months respectively. The Sagona lost her stern section and the destroyer HMS Jervis, one of four alongside her refuelling, was badly damaged. Although the two capital ships sank only in a few feet of water and were eventually raised, they were out of action for over one year.
This represented a dramatic change of fortunes against the Allies from the strategic point of view during the next six months. The Italian fleet had temporarily wrested naval supremacy in the east-central Mediterranean from the Royal Navy.
Valiant was towed to Admiralty Floating Dock 5 on the 21st for temporary repairs and was under repair at Alexandria until April 1942 when she sailed to Durban. By August she was operating with Force B off Africa in exercises for the defence of East Africa and operations against Madagascar. Queen Elizabeth was in drydock at Alexandria for temporary repairs until late June when she sailed for the United States for refit and repairs, which ended the following June. The refit was completed in Britain. Jervis was repaired and operational again by the end of January.