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Human Torpedo Against Gibraltar

by Giulio Poggiaroni


The “X° M.A.S. flotilla” was a special unit of the Italian navy utilising innovative weapons like the human torpedo and the explosive motorboats. The development of such weapons had experienced a long series of stops and go in the 1930s, due to the blindness of the Navy high command in understanding the potential of those weapons. As result, the flotilla was only structured in 1939 and such delays meant that the M.T.M, the human torpedo, as well as the personal breathing devices still needed to be perfectioned. After a failed attempt to attack Alexandria in August 1940, the X° M.A.S. turned its eyes on the other prominent British base in the Mediterranean, Gibraltar.

First attempts

In September 1940, the Submarine “Scirè”, equipped with special cylinders to transport three human torpedos (also known as S.L.C. or “maiali”) departed for the first mission against Gibraltar, under the command of Junio Valerio Borghese. Despite the preparation, the mission was aborted due to adverse meteorological conditions. In October, the Italians tried once again, the Scirè managed to arrive before Gibraltar undetected and release three human torpedos, manned by six frogmen. Among them, there was also the inventor of the S.L.C, Teseo Tesei, who was eager to prove the worthiness of his invention. Soon from the start, all the crew members experienced problems right after detaching from the Scirè. Two crews (including Tesei) were forced to abandon and scuttled their S.L.C. before getting to the enemy harbour. They managed to reach the Spanish coast and were repatriated to Italy in the following weeks. The third crew (Gino Birindelli and Damos Paccagnin) successfully penetrated the inner harbour and got close to battleship HMS Barham. Once they were 70 meters from their target, the S.L.C. stopped working and sunk to the bottom. Birindelli tried to drag the human torpedo alone towards the target, but this proved an effort beyond human capabilities. Birindelli and Paccagnini scuttled the S.L.C. and reached the coast. They tried to mix up with Spanish workers of the port but were identified and captured.

The third attempt against Gibraltar was made in 1941, and yet again the S.L.C. suffered a series of malfunctions that prevented any success. The three crews, however, had managed to penetrate the harbour undetected and safely escaped the area unnoticed.

The first success

Finally, the first success of the S.L.C. materialized in September 1941, during operation “B.G.4”. Once again, the Scirè had managed to arrive undetected in Gibraltar and release the human torpedo. This time no malfunctions occurred and the S.L.C. worked properly, allowing the crews to sink the tanker Fiona Shell and heavily damaging the merchants Derbydale and Durham. The British had reinforced the vigilance of the base and had established constant patrols of motorboats launching depth charges at regular intervals in the water. This prevented the S.L.C. to reach the inner harbour and aiming for the capital ships of the Royal Navy. The experience gathered in B.G.4, as well as the previous failed missions, proved instrumental for the X°M.A.S. to score its biggest success later in December 1941 at Alexandria.

The Gamma men attack

In 1942 the Decima M.A.S. launched several new attacks against Gibraltar, this time also utilising the “Gamma men”. These were highly trained swimmers that carried small explosive charges with them, their tactic was simply to swim towards the target, plant the explosive and swim away. In July 1942 the first operation of this kind took place, with 12 Gamma men smuggled from France to Spain, with destination Algeciras, the port facing Gibraltar. Here the Gamma men reached the secret base hidden in the hull of the interned Italian merchant ship “Olterra”. From here, they reached “Villa Carmela”, a house rented by an Italian diplomat and used as a covert base by the Italian Navy secret service (S.I.S.). Here, they gathered the explosives and launched their assault against Gibraltar. Unseen and Undetected, the twelve men penetrated the harbour and heavily damaged four merchant ships at anchor. They then managed to swim back to Spain and were later repatriated to Italy. 

In September 1942, another raid with only three Gamma men was launched, they managed to sink one merchant ship and swim back to safety.

Human Torpedo Against Gibraltar 2

The last attacks of the “Maiali”

Launching attacks from Olterra and Villa Carmela had proved its effectiveness and thus the X° M.A.S. decided to transform the Olterra into an underwater base for the operations of the “Maiali”. The lower compartment of the ship was transformed, and a large hatch was opened in the hull to allow for the exit of the S.L.C.

The Olterra

The Olterra 2The operators were smuggled to Spain utilising the same channels as for the Gamma men while the S.L.C. were shipped in pieces, disguised as spare parts for the Olterra. Once the base was completed, three attacks were launched with S.L.C. departing from the Olterra. The first one in December 1942 ended up in failure, due to the increased British surveillance, which dropped depth charges at regular intervals in the harbour. Three men were killed, two captured and one escaped. Two other missions carried out in May and August 1943 were successful, with a total of six merchants hit or sunk and no losses among the crews.

The secret base of the Olterra was never discovered by the British until the armistice of September 1943, when finally, they inspected the ship and recovered several S.L.C.  parts, enough to put together one working example and test it at sea.




Bagnasco, E. (2015). I mezzi d’assalto Italiani 1940-1945 (Parte I).

Giorgerini, G. (2007). Attacco dal mare, storia dei mezzi d’assalto della marina italiana.

Toschi, E. (2009 ). La mia avventura con Teseo Tesei .

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