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Decima Flottiglia MAS
Active March 1941–September, 1943
Country Italy Italy
Branch Navy
Type Naval commandos
Role Frogmen, manned torpedoes,
Nickname Xª MAS
Motto "Per il Re e la Bandiera". (For the King and for the Flag)


Equipment SLC "Maiale" torpedoes
MTM "Barchini" motor assault boats
Engagements Souda Bay, Gibraltar, Alexandria, Algiers, sank HMS Queen Elizabeth, HMS Valiant, HMS York, HMS Eridge and 20 merchant ships
Decorations Golden Medal of Military Valour
Individual decorations:
29 Golden Medals of Military Valor
104 Silver Medals of Military Valor
33 Bronze Medals of Military Valor
Vittorio Moccagatta
Ernesto Forza
Junio Valerio Borghese

The Decima Flottiglia MAS (Decima Flottiglia Mezzi d'Assalto, also known as La Decima or Xª MAS) (Italian for "10th Assault Vehicle Flotilla") was an Italian commando frogman unit of the Regia Marina (Italian Royal Navy) created during the Fascist regime.

The acronym MAS also refers to various light torpedo boats used by the Regia Marina during World War I and World War II.[2]

Decima MAS was active during the Battle of the Mediterranean and took part in a number of daring raids on Allied shipping. These operations used surface boats (such as the Sinking of HMS York), manned torpedoes (the Raid on Alexandria) and Gamma Frogmen (against Gibraltar). During the campaign Decima MAS took part in more than a dozen operations which sank or damaged 5 warships and 20 merchant ships totalling 130,000 GRT (Gross Register Tonnage) .

In 1943, after the Italian dictator Benito Mussolini was ousted, Italy left the Tripartite Pact and joined the Allies. Some of the Xª MAS men who were stationed in German-occupied northern Italy enlisted to fight for Mussolini's newly-formed Italian Social Republic (Repubblica Sociale Italiana or RSI) and retained the unit title, but were primarily employed as an anti-partisan force operating on land. Other Xª MAS men in southern Italy or other Allied-occupied areas joined the Italian Co-Belligerent Navy as part of the Mariassalto (Naval Assault) unit.

See Italian commando frogmen for the COMSUBIN frogman corps currently serving the Italian Republic, and for their post-WWII actions.


Historical background

In World War I, on November 1, 1918, Raffaele Paolucci and Raffaele Rossetti of the Regia Marina rode a manned torpedo (nicknamed Mignatta or "leech") into the harbour of Pula, where they sank the Austro-Hungarian battleship SMS Viribus Unitis and the freighter Wien using limpet mines.[3] They had no underwater breathing sets, and thus had to keep their heads above water to breathe. They were discovered and taken prisoner as they attempted to leave the harbor.[4]

In the 1920s, sport spearfishing without breathing apparatus became popular on the Mediterranean coast of France and Italy. This spurred the development of modern swimfins, diving masks and snorkels.

In the 1930s Italian sport spearfishermen began using industrial or submarine-escape oxygen rebreathers, starting scuba diving in Italy.

Unit origins

This new type of diving came to the attention of the Regia Marina which founded the first special forces underwater frogman unit, later copied by the Royal Navy and United States Navy. Capitano di Fregata (Commander) Paolo Aloisi was the first commander of the 1ª Flottiglia Mezzi d'Assalto ("First Assault Vehicle Flotilla"), formed in 1939 as a result of the research and development efforts of Majors Teseo Tesei and Elios Toschi of the naval combat engineers. The two resurrected Paolucci's and Rossetti's concept of manned torpedoes.

In 1941, Commander Vittorio Moccagatta reorganised the First Flotilla into the Decima Flottiglia MAS, and divided the unit into two parts - a surface group operating fast explosive motor boats, and a sub-surface weapons group using manned torpedoes called SLC (siluri a lenta corsa or "slow-running torpedoes", but nicknamed Maiale or "Pig" by their crews), as well as "Gamma" assault swimmers (nuotatori) using limpet mines. Moccagatta also created the frogman training school at the San Leopoldo base of the Italian Naval Academy in Livorno.

Combat record

The Decima MAS saw action starting on June 10, 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 sank the World War I-era Royal Navy battleships HMS Valiant and HMS Queen Elizabeth (both of which after months of work were refloated and returned to action), wrecked the heavy cruiser HMS York and the destroyer HMS Eridge, damaged the destroyer HMS Jervis 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.

Chronicle of operations


Italian Maiale manned torpedo displayed at the Royal Navy Submarine Museum, Gosport, UK.
  • June 10, 1940: Mussolini declared war on Britain.
  • August 22, 1940: While preparing for an attack on the British naval base at Alexandria, Egypt, the Italian submarine Iride (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.[5]
  • September 21, 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 September 30, but was spotted by British destroyer 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.)
  • September 24, 1940: The Italian submarine Sciré, commanded by Commander Junio Valerio Borghese, departed La Spezia carrying three manned torpedoes and four crews, for a planned attack on the British naval base at Gibraltar. The operation was canceled when the British fleet left the harbor before the submarine arrived.
  • October 21, 1940: Sciré departed La Spezia and sailed again to Gibraltar carrying three manned 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 his target, the battleship Barham, and explode but did not cause any 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 return to Italy. Valuable experience was gained in this operation. Gino Birindelli received the Medaglia d'Oro al Valor Militare (MOVM), his second, Damos Paccagnini received the Medaglia d'Argento al Valor Militare (MAVM).


Wreck of HMS York
  • March 25, 1941: The Italian destroyers Crispi and Sella depart Leros island in the Aegean at night, each carrying 3 small (2-ton) MTM (Motoscafo da turismo modificato) motor assault boats of the Decima MAS. Each MTM (nicknamed barchini or "little boats") carries a 300 kg (660 lb) explosive charge in its bow. The one-pilot craft are launched by the destroyers 10 miles off Suda Bay, Crete, where several British Royal Navy warships and auxiliary ships are at anchor. The MTMs are specially equipped to make their way through obstacles such as torpedo nets; the pilot steers the assault craft in a collision course at his target ship, and jumps from his boat before impact and warhead detonation. Once inside the bay, the six boats locate their targets: the heavy cruiser HMS York, a large tanker (the Norwegian Pericles of 8,300 tons), another tanker, and a cargo ship. Two MTMs hit the York amidships, flooding her aft boilers and magazines. The Pericles is severely damaged and settles on the bottom, while the other tanker and the cargo ship are sunk. The other barchini apparently miss their intended targets, and one of them is stranded on the beach. All six of the daring Italian sailors are captured. The disabled York is later scuttled with demolition charges by her crew before the German capture of Crete, while the Pericles sinks in April 1941 enroute to Alexandria.
  • May 25, 1941: The Sciré departs La Spezia carrying three manned torpedoes. At Cadiz, Spain it secretly loads eight Decima MAS crewmen. At Gibraltar, they find no warships because the Renown, Ark Royal and Sheffield have been ordered to the Atlantic to hunt the German battleship Bismarck. The manned torpedoes once again experience technical problems as they unsuccessfully attempt to attack a freighter. The crew return to Italy via Spain.
  • June 26, 1941: An attack on Malta similar to the July 26, 1941 operation (see below) is planned but is canceled due to bad weather.[6]
  • July 26, 1941: Two Maiale and ten MAS boats (including six barchini') unsuccessfully attack the port of Valletta, Malta. The force is detected early on by a British radar installation, but the British coastal batteries hold their fire until the Italians approach to close range. 15 Decima MAS crewmen are killed (including Commander Moccagatta) and 18 captured. Teseo Tesei and Petty Officer Alcide Pedretti on one torpedo die by Fort St. Elmo as they attempt to destroy the outer defenses of the harbor. Lieutenant Franco Costa and Sgt. Luigi Barla on the other torpedo become lost, scuttle their craft and swim ashore at St. George's Bay two miles NW of Valletta; their Maiale is recovered by the British, the first example they have examined.[6] All 6 MTMs, both SLCs and two MAS boats are lost, one of them found adrift in open seas by the British and towed to port by a seaplane. This disaster forces the unit to make a huge reassessment of its operations. Commander Enrico Forza is named as commander of the Decima MAS, and Borghese becomes leader of the sub-surface weapons group.[7]
  • September 10, 1941: The Sciré departs La Spezia carrying three manned torpedoes. At Cadiz, Spain, it secretly loads eight crewmen for them. At Gibraltar, the manned torpedoes sink three ships: the tankers Denbydale and Fiona Shell and the cargo ship Durham. All six crewmen swim to Spain and return safely to Italy, where they are decorated, as are the crew of the Sciré.
  • December 3, 1941: The Sciré departs La Spezia carrying three manned torpedoes to conduct what became the Raid on Alexandria (1941). At the island of Leros in the Aegean Sea, six Decima MAS crewmen come aboard, including Lieutenant Luigi Durand de la Penne. On December 19 Sciré releases the manned torpedoes 1.3 miles from Alexandria commercial harbor, and they enter the harbor when the British open their defenses to let three of their destroyers pass. After many difficulties, de la Penne and his crewmate Emilio Bianchi successfully attach a limpet mine under HMS Valiant, but have to surface as they attempt to leave and are captured. Questioned, they refuse to speak, and are detained in a compartment aboard Valiant. Fifteen minutes before the explosion, de la Penne asks to speak to the Valiant's captain, informs him of the imminent explosion, but refuses to give other information. He is returned to the compartment, but both he and Bianchi are not injured by the detonation of the mine. The other four torpedo-riders are also captured, but their mines sink the Valiant, the battleship Queen Elizabeth, the Norwegian tanker Sagona and badly damaged the destroyer HMS Jervis. The two battleships sank in only a few feet of water and were subsequently refloated, nevertheless they were out of action for over one year.


  • April 29, 1942: The Italian submarine Ambra departs La Spezia carrying three manned torpedoes. At Leros it secretly loads six crewmen for them. On May 14 Ambra reaches Alexandria to sink a British floating dock, but the Ambra was spotted and could not sink anything. All six torpedo-riders were captured.
  • July 1942: Italian frogmen set up in 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.
  • July 13, 1942: Twelve Italian frogmen swam from the Algeciras coast into Gibraltar harbor and set explosives, and then returned safely. They sank four ships.
  • August 29, 1942: Off El Daba, Egypt. The Hunt class destroyer HMS Eridge was torpedoed at close range by an MTSM, a torpedo-carrying version of the MTM. Six of her crew were lost. HMS Eridge was towed to Alexandria, but soon after was declared a "constructive total loss", and was scrapped in 1946.[8]
  • December 4, 1942: The Ambra left La Spezia to attack Algiers, carrying frogmen and two manned torpedoes. Ten frogmen carrying limpet mines swam with the manned torpedoes, but because of the distance they did not reach the harbor, but attacked ships outside it, sank two and damaged two others.
  • December 17, 1942: Six Italians on three torpedoes left the Olterra to attack the three British warships Nelson, Formidable, and Furious 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 (who dived with Davis Escape Sets and (up to here) breaststroke swimming and no fins) (Sydney Knowles and Commander Lionel Crabb). 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.


  • May 8, 1943: Three Italian manned torpedoes left the tanker Olterra to attack Gibraltar in bad weather and sank two British freighters and an American Liberty ship. All returned safely to the Olterra.
This drawing shows a Norwegian tanker broken in two by manned torpedoes launched from the Italian base-ship Olterra, August 1943
  • May 1943 : Borghese becomes unit commander when Forza returns to sea [9]
  • July 25, 1943: Italian dictator Benito Mussolini was replaced by Field Marshal Pietro Badoglio as the head of the Italian government.
  • July 1943: Xª MAS single frogman sank or crippled the ship Kaituna (10,000 tons) at Mersin in Turkey.[10]
  • August 3, 1943: In the evening, three Italian manned 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 is captured.
  • August 1943: Xª MAS single frogman sank or crippled the Norwegian cargo ship Fernplant (7000 tons) at İskenderun in Turkey.[10]


  • September 8, 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

Date Place Ship(s)
March 1941 Suda Bay Cruiser HMS York (disabled, wrecked after salvage abandoned)

Tanker Pericles
Tanker (probably)
Steamship (probably)

September 1941 Gibraltar Tanker Denby Dale

Tanker Fiona Shell
Motorship Durham

December 1941 Alexandria Battleship Queen Elizabeth (repaired and returned to action)

Battleship Valiant (repaired and returned to action)
Tanker Sagona
Destroyer Jervis (in dock for 6 weeks for repairs)

June 1942 Sebastopol Military transport (Russian)

Small craft (Russian)
Two Russian submarines

July 1942 Gibraltar Steamship Meta
SS Empire Snipe (out of service to October 1942)

Steamship Shuma
Steamship Baron Dougla

August 1942 El Daba Destroyer HMS Eridge (disabled, used as base ship thereafter)
September 1942 Gibraltar Steamship Raven's Point
December 1942 Algiers Steamship Ocean Vanquisher
Steamship Berta
Steamship Armattan
Tanker Empire Centaur (repaired)

Military Transport N.59 (U.S.)

May 1943 Gibraltar Steamship Pat Harrison (U.S.)
Steamship Mahsud
Steamship Camerata
July 1943 Alexandretta Motorship Orion (Greek)
July 1943 Mersina Motorship Kaituna
August 1943 Alexandretta Motorship Fernplant (Norwegian)
August 1943 Gibraltar Steamship Harrison Gray Otis (U.S.)
Steamship Stanridge
Tanker Thorshøvdi (Norwegian)

Successor units

Following the armistice of Italy on September 8, 1943, the Xª MAS was disbanded. The Badoglio government in the south of Italy under Allied occupation declared war on Germany and became a co-belligerent. Some Decima MAS sailors joined the Allied cause to fight against Nazi Germany and what remained of the Axis as part of the Italian Co-Belligerent Navy. A new unit was formed, led by Forza and joined by some of the pioneers such as de la Penne newly released from British POW camps. The new unit was named Marassalto, but continued to be an elite naval force mounting special operations at sea.

In the north German occupied north Mussolini set up an Italian Socialist Republic Italian Social Republic (Repubblica Sociale Italiana, or RSI) to continue the war as part of the Axis. Led by Borghese Decima Flottiglia was revived, as part of the National Republican Navy (Marina Nazionale Repubblicana) of the RSI. with its headquartered in Caserma del Muggiano, La Spezia. By the end of the war, it had over 18,000 members, and although Borghese conceived it as a purely military unit, it gained a reputation as a savage pro-fascist, anti-communist, anti-resistance force in land campaigns alongside the German Army (Wehrmacht Heer), under the command of SS General Karl Wolff.


Active October 1943–April 26, 1945
Country Italy Kingdom of Italy
Branch Italian Co-Belligerent Navy
Type Naval commandos
Role Frogmen, manned torpedoes
Equipment Chariot
Engagements Raid on Genoa
Raid on La Spezia
Ernesto Forza

The Mariassalto was set up at Taranto alongside the British frogman force in the Mediterranean. Forza was pleased to demonstrate Italian expertise in this area to the British [11], and the group was also keen to be in action, that if they were caught they would almost certainly be shot. [12] However Allied naval supremacy had left a dearth of targets for the group.

In June 1944 came an opportunity to take action, in Operation QWZ, a joint mission against targets in La Spezia harbour. The attack was against the Italian cruisers Bolzano and Gorizia, which had been taken by the Germans after the Italian surrender. This was to thwart a German plan to sink them where they would block the harbour entrance. The mission also aimed to attack German U-boats in the harbour. British Charioteers would attack the cruisers whilst Mariassalto's Gamma Frogmen would attack U-boats penned in the harbour. On 2 June 1944 the Italian destroyer Grecale sailed from Bastia in Corsica to La Spezia carrying three speedboats, and Italian frogmen including Luigi Durand De La Penne, and two British chariots. One chariot broke down and was abandoned, though the other successfully sank Bolzano. However the Gamma men were unsuccessful in their attack on the U-boat pens. All the participants escaped to link with partisan groups on land.[13]

In April 1945 a final mission, Operation Toast, was planned. This was aimed at sinking the aircraft carrier Aquila, just completed in Genoa. For this the Mariassalto men would make use of a British Chariot, as they had none of their own SLC available. On 18 April 1945 the destroyer Legionario, carrying two motorboats equipped with chariots sailed for Genoa led by G Manisco. One chariot broke down and had to be abandoned, but the other team succeeded in laying a charge under Aquila. The charge exploded as planned, but the ship remained afloat, and was later sunk by the Germans as a blockship to the harbour. [14]

Decima MAS (RSI)

Decima Flottiglia MAS
Badge of the Xª MAS (Under RSI)
Active September 1943–April 26, 1945
Country Italy Italian Social Republic
Branch Navy
Type Naval commandos
Role anti-partisan
Nickname Xª MAS
Motto Memento Audere Semper (Remember to dare always)
Junio Valerio Borghese

Some Xª MAS men who were in German-occupied Italy remained part of the Axis forces, joining the Italian Social Republic under the command of Captain Borghese. The reputation of the Xª MAS and Captain Borghese enabled him to negotiate an agreement with the German forces that gave the Xª MAS significant autonomy, allowed them to fight under an Italian flag (under the command of the Germans), and not to be employed against other Italians. Borghese was recognized as the leader of the corps. [15]


The main themes in the Xª MAS's ideology became "honour" in defending Italy from the "betrayal" of the armistice with the Allies, strong anti-semitism in the wake of stronger Nazi influence, and a call to defend the territorial integrity of Italy against the Allies. This was quite ironic, as the Third Reich was already annexing northeastern Italian territories and integrating them directly into the Reich as the Prealpine Operations Zone and Operational Zone Adriatic Coast.

The corps had its own weekly magazine, L'orizzonte ("The Horizon"), in which authors such as Giovanni Preziosi wrote vehemently anti-Semitic articles about Jewish conspiracies. The magazine had problems in its distribution, as it was thought that Borghese's popularity among the Fascist hardliners might reduce Mussolini's influence. [16]

Relations with the RSI

Relationships with the Italian Social Republic were not easy. On January 14, 1944 Mussolini arrested Borghese while receiving him in Garniano, in order to gain direct control of the Xª MAS. Word of the arrest reached the officers of the Decima, who considered marching on Mussolini's capital at Salò. However, the German command used their influence to have Borghese released, as they needed the equipment, expertise and manpower of the Xª MAS as an anti-partisan force.[17]

Naval actions

The Xª MAS (RSI) took little part in the war at sea. Its equipment had been abandoned in the south, and its naval activities were frustrated by Allied action. [18] In November 1944 Four frogmen (Malacarne, Sorgetti, Bertoncin, Pavone), who had stayed under German command, were delivered by fast motorboat and swam into Livorno harbor to set up a secret sabotage base, but were captured. [19]

Anti-partisan actions

Ferruccio Nazionale, Italian partisan hanged by the Xª MAS. The sign says: "He attempted to shoot the Decima"

The Germans used the Decima mostly in anti-partisan actions on land, rather than against the Allies at sea. Their anti-partisan actions usually took place in small villages, where the partisans were stronger. Some examples:

  • Forno: 68 persons, mostly civilians and some partisans, were killed by a combination of German and Xª MAS forces. [20]
  • Guadine: Random violence to terrorize a population believed to be supporting the rebels, almost complete destruction of the village by fire.[21]
  • Borgo Ticino: Together with the SS, murder of 12 civilians, pillage and destruction of the village by fire on the grounds that three German soldiers had been wounded by partisans.[22]
  • Castelletto Ticino: In order to give "a demonstration of firmness" against "crime", a Xª MAS officer had five petty criminals publicly gunned down, having taken care to gather a large crowd in order to terrorise them.[23]
  • Crocetta del Montello: Episodes of torture with whips and gasoline and summary executions of partisans. [24]

However, the Xª MAS units also earned a good combat reputation fighting on the frontline against the Allies at Anzio and on the Gothic Line. In the last months of the war Xª MAS units were dispatched to the eastern Italian border against Tito's partisans. On April 26, 1945 in what is now the Piazza della Repubblica in Milan, Borghese finally ordered the Xª MAS to disband. He was soon arrested by partisans, but rescued by OSS officer James Angleton, who dressed him in an American uniform and drove him to Rome for interrogation by the Allies. This left many of Borghese's previous companions in the hands of the partisan resistance[citation needed]. Borghese was tried and convicted of war crimes, sentenced to 12 years imprisonment, but released from jail by the Italian Supreme Court in 1949. The Americans were keenly interested in infiltrating the Italian Communist groups, something which Borghese had done, and he was enlisted to help create counterintelligence units for the Americans.

Organization of RSI Xa MAS

  • Naval units
    • Combat swimmers and frogmen
  • 1st Combat Group
    • 'Barbarigo', 'Lupo' battalions
    • 'Nuotatori Paracadutisti' Parachute battalion
    • 'Colleoni" artillery battalion
    • 'Freccia' Engineer battalion - 1st company only
  • 2nd Combat Group
    • 'Valanga' Assault Engineer battalion
    • 'Sagittario', 'Freccia', and 'Fulmine' battalions
    • 'Castagnacci' recruitment and replacement battalion
    • 'Da Giussano' artillery battalion
    • 'Freccia' engineer battalion - 2nd and 3rd companies
  • 8 independent infantry battalions
  • 5 independent infantry companies
  • Women's Auxiliary Service

After 1945

See Italian commando frogmen.

In popular culture

See also


More information about the Decima Mas is in these books:-

  • "Frogmen First Battles" by retired U.S Captain William Schofield's book (ISBN 0-8283-2088-8)
  • "The Black Prince and the Sea Devils: The Story of Valerio Borghese and the Elite Units of the Decima Mas", by Jack Greene and Alessandro Massignani, Cambridge, Mass.: Da Capo Press, 2004 284 pages, hardcover (ISBN 0-306-81311-4)
  • "Sea Devils" by J. Valerio Borghese, translated into English by James Cleugh, with introduction by the United States Naval Institute (ISBN 1-55750-072-X)
  • Paul Kemp : Underwater Warriors (1997) ISBN 1 85409 455 6


External links

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