The Decima MAS saw action starting on 10 June 1940, when Fascist Italy entered World War II. In more than three years of war, the unit destroyed some 72,190 tons of Allied warships and 130,572 tons of Allied merchant ships. Personnel from the unit seriously damaged the World War I-era
Royal Navy battleships and (both of which were out of action for months), wrecked the
heavy cruiser and the
destroyer , damaged the destroyer and sank or damaged 20
merchant ships, including supply ships and tankers. During the course of the war, the Decima MAS was awarded the
Golden Medal of Military Valour and individual members were awarded a total of 29
Golden Medals of Military Valour, 104
Silver Medals of Military Valour and 33
Bronze Medals of Military Valour.
1940 " displayed at the
Royal Navy Submarine Museum,
Gosport, UK. • 10 June 1940:
Benito Mussolini declared war on
United Kingdom. • 22 August 1940: While preparing for an attack on the British naval base at
Alexandria,
Egypt, the Italian submarine (carrying four
Maiale and five two-man crews) and the support ship
Monte Gargano were attacked and sunk in the
Gulf of Bomba off
Tobruk,
Libya, by British land-based
Fairey Swordfish torpedo bombers. Teseo Tesei survived the attack, but casualties among the submarine crew were heavy. • 21 September 1940: The Italian submarine
Gondar departed
La Spezia for Alexandria, carrying three
Maiale and four two-man crews. The
Gondar reached Alexandria on the evening of 30 September, but was spotted by British and Australian destroyers, which attacked. Severely damaged, it was forced to the surface and scuttled by the crew. They were captured, along with the Decima MAS crewmen (including Elios Toschi). • 24 September 1940: The Italian submarine , commanded by Commander
Junio Valerio Borghese, departed La Spezia carrying three human torpedoes and four crews, for a planned attack on the British naval base at
Gibraltar. The operation was cancelled when the British fleet left harbour before the submarine arrived. • 21 October 1940:
Sciré departed La Spezia and sailed again to Gibraltar carrying three human torpedoes and four crews. The
Decima MAS frogmen entered the harbour, but were unable to attack any ships due to technical problems with the torpedoes and breathing equipment. Only one human torpedo managed to get close to a target, the battleship
Barham. The charge exploded but did not cause significant damage. The two crewmen, Gino Birindelli and Damos Paccagnini, were captured by the British. The other four (including Teseo Tesei) manage to reach
Spain and returned to Italy. Valuable experience was gained in this operation by the Decima.
Gino Birindelli received the ''
Medaglia d'Oro al Valor Militare (MOVM), his second, Damos Paccagnini received the Medaglia d'Argento al Valore Militare'' (MAVM).
1941 , moored alongside • 25 March 1941: The Italian destroyers and departed
Leros island in the
Aegean at night, each carrying 3 small (2-ton)
Motoscafo da Turismo motor assault boats of the Decima MAS. Each MT (nicknamed
barchini or "little boats") carried a 300 kg (660 lb) explosive charge in its
bow. The one-pilot craft were launched by the destroyers 10 miles off
Suda Bay,
Crete, where several British Royal Navy warships and auxiliary ships were at anchor. The MTs were specially equipped to make their way through obstacles such as
torpedo nets; the pilot steered the assault craft in a collision course at his target ship, and jumped from his boat before impact and warhead detonation. Once inside the bay, the six boats located their targets: the
heavy cruiser , a large tanker (the Norwegian
Pericles of 8,300 tons), another tanker, and a cargo ship. Two MTMs hit
York amidships, flooding her aft boilers and magazines.
Pericles was severely damaged and settled on the bottom, while the other tanker and the cargo ship were sunk. The other
barchini apparently missed their intended targets, and one of them was stranded on the beach. All six of the Italian sailors were captured. The disabled
York was later scuttled in shallow waters with demolition charges by her crew before the
German capture of Crete, while
Pericles sank in April 1941 en route to Alexandria. • 25 May 1941: The
Sciré departed La Spezia carrying three human torpedoes. At
Cádiz,
Spain it secretly embarked eight Decima MAS crewmen. At Gibraltar, they found no warships because , , and had been ordered to the
Atlantic to hunt the German battleship . The torpedoes once again experienced technical problems as they unsuccessfully attempted to attack a freighter. The crew returned to Italy via Spain. • 26 June 1941: An attack on Malta similar to the 26 July 1941 operation (see below) was planned but was canceled due to bad weather. in
Valletta, which was destroyed in the attack of 26 July 1941 • 26 July 1941: Two
Maiale and ten MAS boats (including six
barchini)
unsuccessfully attacked the port of
Valletta,
Malta. The force was detected early on by a British
radar installation, but the British
coastal batteries held their fire until the Italians approached to close range. Fifteen
Decima MAS crewmen were killed (including Commander Moccagatta), and 18 were captured. Teseo Tesei and
Petty Officer on one torpedo died by
Fort St. Elmo as they attempted to destroy the outer defenses of the harbour.
Lieutenant Franco Costa and
sergeant Luigi Barla on the other torpedo became lost, scuttled their craft, and swam ashore at St. George's Bay two miles NW of Valletta. Their
Maiale was recovered by the British, becoming the first example they had been able to examine.) boats were lost, one of them being found adrift in open seas by the British and towed to port by a seaplane. This disaster forced the unit to make a huge reassessment of its operations. Commander
Ernesto Forza was named as commander of the Decima MAS, and Borghese became leader of the sub-surface weapons group. • 10 September 1941: The
Sciré departed La Spezia carrying three human torpedoes. At Cádiz, Spain, it secretly embarked eight crewmen for them. At Gibraltar, the torpedoes sank three ships: the
tankers Denbydale and
Fiona Shell, and the
cargo ship Durham. All six crewmen swam to Spain and returned safely to Italy, where they were decorated, as were the crew of
Sciré. • 3 December 1941:
Sciré departed La Spezia carrying three human torpedoes to conduct what became the
Raid on Alexandria (1941). At the island of
Leros in the
Aegean Sea, six Decima MAS crewmen came aboard, including
Lieutenant Luigi Durand de la Penne. On 18 December
Sciré released the torpedoes 1.3 miles from Alexandria commercial harbour, and they entered the harbour when the British opened the boom defence to let three of their
destroyers pass. After many difficulties, de la Penne and his crewmate Emilio Bianchi successfully attached a limpet mine under , but had to surface as they attempted to leave, and were captured. They refused to answer when questioned and were detained in a compartment aboard
Valiant. Fifteen minutes before the explosion, de la Penne asked to speak to the
Valiants captain and informed him of the imminent explosion but refused to give other information. He was returned to the compartment and neither he nor Bianchi were injured by the detonation of the mine. The other four torpedo-riders were also captured, but their mines seriously damaged
Valiant and the battleship , sank the Norwegian tanker
Sagona, and badly damaged the destroyer . The two battleships were subsequently repaired, but were out of action for over a year.
1942 • 29 April 1942: The Italian submarine
Ambra departed La Spezia carrying three human torpedoes. At
Leros six crewmen were secretly loaded for them. On 14 May
Ambra reached Alexandria and sank a British floating dock. The
Ambra was spotted and could not sink anything. All six torpedo-riders were captured. • July 1942: Italian frogmen set up a secret base in the Italian tanker
Olterra which was
interned in
Algeciras near Gibraltar. All materials had to be moved secretly through Spain and this limited operations. • 13 July 1942: Twelve Italian frogmen swam from the Algeciras coast into Gibraltar harbour and set explosives, and then returned safely. Four ships were sunk. • 10 August 1942: The
Italian submarine Scirè was sunk by
HMS Islay while attempting to attack the port of
Haifa in British
Palestine. She had 11 frogmen on board. • 29 August 1942: Off
El Daba, Egypt. The was torpedoed at close range by an
MTSM, a torpedo-carrying version of the
MTM. Six of her crew were lost. was towed to Alexandria, but soon after was declared a "constructive total loss", and was scrapped in 1946. • 4 December 1942: The
Ambra left
La Spezia to attack
Algiers, carrying frogmen and two human torpedoes. Ten frogmen carrying limpet mines swam with the human torpedoes, but because of the distance, they did not reach the harbour, but attacked ships outside it, sank two and damaged two others. • 17 December 1942: Six Italians on three torpedoes left the
Olterra to attack the three British warships , , and in Gibraltar. A British patrol boat killed one torpedo's crew (Lt. Visintini and Petty Officer Magro) with a
depth charge. Their bodies were recovered, and their
swimfins were taken and used by two of Gibraltar's British guard divers. Another British patrol boat spotted another torpedo, and chased and shot at it and captured its two crewmen. The remaining torpedo returned to the
Olterra without its rear rider.
1943 • 8 May 1943: Three Italian human torpedoes left the
Olterra to attack Gibraltar in bad weather and sank two British freighters and an American
Liberty ship. All returned safely to the
Olterra. es launched from the Italian base-ship
Olterra, August 1943 • May 1943: Borghese becomes unit commander when Forza returned to sea • 25 July 1943: Italian dictator
Benito Mussolini was replaced by Field Marshal
Pietro Badoglio as the head of the Italian Government. • 9 July 1943: Xª MAS single frogman sank or crippled the ship
Kaituna (4,917 tons) at
Mersin in
Turkey. • 3 August 1943: In the evening, three Italian human torpedoes left the
Olterra to attack Gibraltar. They sank three cargo ships, one of them an American
Liberty and returned to the
Olterra. One of the Italian divers was captured. • 1 August 1943: Xª MAS single frogman sank or crippled the Norwegian cargo ship
Fernplant (7,000 tons) at
İskenderun in
Turkey.
Armistice • 8 September 1943: The new Badoglio government of Italy signed an armistice with the Allies. The
Olterra was towed into Gibraltar, and the British found what had happened in it. Further attacks on Gibraltar using the new and larger replacement for the SLC (the
Siluro San Bartolomeo type), and a planned raid on
New York City were called off due to the Italian surrender.
Summary of Allied ships sunk or damaged by Decima MAS ==Successor units==