The Decima Flottiglia MAS (Decima Flottiglia Motoscafi Armati Siluranti, also known as La Decima or Xª MAS) (Italian for "10th Torpedo-Armed Motorboat Flotilla") was an Italian flotilla, with marines and commando frogman unit, of the Regia Marina (Royal Italian Navy). The acronym MAS also refers to various light torpedo boats used by the Regia Marina during World War I and World War II.
Decima MAS was active during the Battle of the Mediterranean and took part in a number of daring raids on Allied shipping. These operations involved surface speedboats (such as the raid on Souda Bay), human 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 five warships (totalling 78,000 tons) and 20 merchant ships (totalling 130,000 GRT).
In 1943, after the Italian dictator Benito Mussolini was ousted, Italy left the Tripartite Pact. Some of the Xª MAS men who were stationed in German-occupied northern and central 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.
Historical background In World War I, on 1 November 1918, Raffaele Paolucci and Raffaele Rossetti of the Regia Marina rode a human torpedo (nicknamed Mignatta or "leech") into the harbour of Pula, where they sank the battleship Jugoslavija, of the navy of the State of Slovenes, Croats and Serbs, formerly the Austro-Hungarian battleship , and the freighter Wien using limpet mines. 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 harbour.
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 and equipment 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 human torpedoes.
In 1941, Commander Vittorio Moccagatta re-organised 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 human 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.
equipment
(SLC)
The Siluro Lenta Corsa (SLC, slow speed torpedo), known as Maiale (pig), was designed by Tesei and Toschi during 1935 and 1936. By late 1939 about eleven were ready and in July 1940 the production version, Series 100, began to arrive. In 1941 the improved Series 200 became ready for use. The standard torpedo with double propellers was changed to one larger propeller in a cowling; seats for a two-man crew were installed, with shields housing the controls. The SLC weighed and was long. The electric motor moved the at at a maximum depth of . At the target the crew detached a -long warhead with of explosive, detonated by a timer. The crews the Gamma frogmen wore Belloni rubberised suits with a closed-circuit re-breathing apparatus to avoid bubbles. The Gamma frogmen carried explosive charges, five (bedbugs) or two , (little trunks) and attached them to a ship's hull, with a timed detonation.
(MTL)
and SLCs needed transport close to the target because the re-breather lasted no more than six hours and had a range of only at full speed and a maximum of at cruising speed. The modified destroyers and , had carried the MTM used in the successful Raid on Souda Bay (25/26 March 1941). The (MTL, slow transport motorboat) was a wooden-hulled boat long by wide, to carry close to the target. The MTL had a range of only cruising at , few were built and they were rarely used. Surface transport gave way to submarines; early in 1940 the began tests as a transport. The maximum depth of submersion was only ; was converted in July 1940 but was sunk on 21 August. was sunk on 30 September, even though the three cylinders could be flooded, allowing the boat to reach a depth of .
(MT/MTM)
The first (MT) that became known as (little boats) were built in late 1938, six MT being delivered in early 1939. An improved version (MTM) tested in November 1940, was long. Both types carried an explosive charge of in the bows at up to . The MTM was fitted with a seat back/life raft behind the pilot for him to float on after dropping off the MTM, while waiting to be rescued. Twelve MTs were built and about forty MTMs. Early in 1941, a smaller was built with a height of to fit inside the deck cylinders of submarines with the same explosive charge but they were never used in this manner.
(MTS)
The (MTS, torpedo motorboat), was a small boat carrying one or two modified torpedoes, the MTS being more manoeuvrable than the usual . The first MTS, of early 1941, could reach with a range of . The was assisted by MAS boats, which by June 1940, had fifty Class 500 MAS and another 25 in 1941 in four versions. The Class 500 was long by wide at the beam, with a displacement of . The MAS had a crew of 9 to 13 men and had two torpedoes, 6–10 depth charges and a heavy machine-gun (replaced in 1941 with a Breda 20 mm cannon). The MAS could move at and had a range of .
List of + equipmentNameAcronymEnglish translationNotes—Gamma MenFrogmen sabotage specialistsMASArmed torpedo motorboatSimilar to a British Motor torpedo boat (MTB)MTLeisure motorboatExplosive assault boat, 12 builtMTLSlow transport motorboatKnown as (little boats)MTMImproved explosive assault motorboatForty builtMTRSmall assault motorboatMTSTorpedo motorboatMTSMImproved torpedo motorboatSLCSlow human torpedo
Combat record 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
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
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.pp. 6–11, issue 39, Historical Diving Times