View source for Decima Flottiglia MAS

{{short description|Italian naval commando frogman unit of the Fascist era}}
{{use dmy dates|date=June 2024}}
{{Infobox military unit
| unit_name                     = Decima Flottiglia MAS
| image                         = File:Teseo Tesei.jpg
| caption                       = [[Teseo Tesei]], Italian naval officer who organized the Decima Flottiglia MAS and pioneered the use of underwater raids
| start_date                    = March 1941
| end_date                      = September 1943
| country                       = {{flagcountry|Kingdom of Italy}}
| branch                        = {{navy|Kingdom of Italy}}
| type                          = [[Marines]]<br />[[Commando frogman]]
| role                          = [[Human torpedo]]<br />[[Raid (military)|Raiding]]<br />[[Sabotage]]
| size                          = 
| command_structure             = 
| garrison                      = 
| garrison_label                = 
| nickname                      = Xª MAS
| patron                        = 
| motto                         = "Memento Audere Semper" (Remember to always be bold)
<ref>[http://www.marina.difesa.it/storia/movm/parte01/movm107.asp] {{webarchive |url=https://web.archive.org/web/20070625093613/http://www.marina.difesa.it/storia/movm/parte01/movm107.asp |date=25 June 2007 }}</ref>
| colours                       = 
| colours_label                 = 
| march                         = Inno della Xª MAS
| mascot                        = 
| equipment                     = [[Human torpedoes|SLC "''Maiale''" torpedoes]]<br />[[MT explosive motor boat|MTM "''Barchini''" motor assault boats]]
| equipment_label               = Equipment
| battles                       = [[Sinking of HMS York|Souda Bay]], [[Auxiliary ship Olterra|Gibraltar]], [[Raid on Alexandria (1941)|Alexandria]], [[Raid on Algiers|Algiers]], sank {{HMS|York|90|6}} and 20 merchant ships
| anniversaries                 = 
| decorations                   = [[Gold Medal of Military Valor|Golden Medal of Military Valour]]<br />'''Individual decorations:'''<br />29 [[Gold Medal of Military Valor|Golden Medals of Military Valor]]<br />104 [[Silver Medal of Military Valor|Silver Medals of Military Valor]]<br />33 [[Bronze Medal of Military Valor|Bronze Medals of Military Valor]]
| battle_honours                = 
| disbanded                     = <!-- Commanders -->
| commander1                    = 
| commander1_label              = 
| commander2                    = 
| commander2_label              = 
| commander3                    = 
| commander3_label              = 
| notable_commanders            = [[Mario Giorgini]]<br />[[Vittorio Moccagatta]]<br />[[Ernesto Forza]]<br />[[Junio Valerio Borghese]]
<!-- Insignia -->| identification_symbol         = 
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}}

{{Campaignbox Mediterranean Naval WW2}}
The '''''Decima Flottiglia MAS''''' (''Decima Flottiglia Motoscafi Armati Siluranti'', also known as '''''La Decima''''' or '''Xª MAS''') ([[Italian language|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 (motorboat)|MAS]]'' also refers to various light [[torpedo boat]]s used by the Regia Marina during [[World War I]] and [[World War II]].<ref>[http://www.historynet.com/wars_conflicts/military_technology/3033126.html?featured=y&c=y] {{webarchive|url=https://web.archive.org/web/20071219030423/http://www.historynet.com/wars_conflicts/military_technology/3033126.html?featured=y&c=y|date=19 December 2007}}</ref>

''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 torpedo]]es (the [[Raid on Alexandria (1941)|raid on Alexandria]]) and ''Gamma'' [[frogmen]] (against [[Military history of Gibraltar during World War II#Xª MAS: 1940–1943|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 [[Fall of the Fascist regime in Italy|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 (military)|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 [[SMS Viribus Unitis|''Jugoslavija'']], of the navy of the [[State of Slovenes, Croats and Serbs]], formerly the [[Austro-Hungarian Navy|Austro-Hungarian]] [[battleship]] {{SMS|Viribus Unitis||6}}, and the [[Cargo ship|freighter]] ''Wien'' using [[limpet mine]]s.<ref name=quick>{{cite journal |last=Quick |first=D. |title=A History Of Closed Circuit Oxygen Underwater Breathing Apparatus |journal=Royal Australian Navy, School of Underwater Medicine. |volume=[[RANSUM]]-1-70 |year=1970 |url=http://archive.rubicon-foundation.org/4960 |access-date=2009-03-20 |archive-date=2008-05-09 |archive-url=https://web.archive.org/web/20080509072728/http://archive.rubicon-foundation.org/4960 |url-status=usurped }}</ref> They had no [[Scuba set|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.<ref>{{cite web|url=http://www.worldwar1.com/sfvu.htm |title=Trenches on the Web – Special Feature: Assault on the Viribus Unitis |publisher=Worldwar1.com |access-date=2015-08-18}}</ref>

In the 1920s, sport [[spearfishing]] without breathing apparatus became popular on the [[Mediterranean]] coast of [[France]] and Italy. This spurred the development of modern [[swimfin]]s, [[diving mask]]s and [[Snorkel (swimming)|snorkel]]s.{{fact|date=December 2024}}

In the 1930s Italian sport spearfishermen began using industrial or submarine-escape oxygen [[rebreather]]s, starting [[scuba diving]] in Italy.{{fact|date=December 2024}}

==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 [[British commando frogmen|Royal Navy]] and [[Underwater Demolition Team|United States Navy]]. ''[[Frigate captain|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 [[Major (rank)|Major]]s [[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 torpedo]]es 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]].

=== {{lang|it|Decima MAS}} equipment ===

==== {{lang|it|Siluro lenta corsa}} (SLC) ====
[[File:Maiale_SLC.jpg|thumb|{{center|A SLC ({{lang|it|Maiale}} at the {{lang|it|Museo}} {{ill|Sacrario delle Bandiere|it}} {{lang|it|delle Forze Armate}}, Rome.}}]]
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 {{cvt|533|mm}} 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 {{cvt|1.3|–|1.4|LT}} and was {{cvt|22|–|24|ft}} long. The {{cvt|1.6|hp}} electric motor moved the {{lang|it|maiale}} at {{cvt|2|–|3|nmi}} at a maximum depth of {{cvt|50|ft}}. At the target the crew detached a {{cvt|6|ft}}-long warhead with {{cvt|230|to|260|kg|order=flip}} of explosive, detonated by a timer. The {{lang|it|maiale}} 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 {{cvt|4.5|kg|order=flip}} {{lang|it|cimici}} (bedbugs) or two {{cvt|12|kg|order=flip}} {{lang|it|bauletti}}, (little trunks) and attached them to a ship's hull, with a timed detonation.{{sfn|Crociani|Battistelli|2013|pp=12–13}}{{efn|Students at the Gamma training school, which began in September 1940, had a stringent ten-month course; about fifty graduates undertook operations during the war.{{sfn|Crociani|Battistelli|2013|p=12}}}}

==== {{lang|it|Motoscafo trasporto lento}} (MTL) ====
[[File:Waterproof_container_for_SLC_Assault_Craft.JPG|right|thumb|{{center|Container for a {{lang|it|maiale}} to be attached to the deck of a submarine}}]]
{{lang|it|Maiali}} and SLCs needed transport close to the target because the re-breather lasted no more than six hours and {{lang|it|maiali}} had a range of only {{cvt|4|nmi}} at full speed and a maximum of {{cvt|15|nmi}} at cruising speed.{{sfn|Crociani|Battistelli|2013|pp=12–13}} The modified destroyers {{ship|Italian destroyer|Francesco Crispi||2}} and {{ship|Italian destroyer|Quintino Sella||2}}, had carried the MTM used in the successful [[Raid on Souda Bay]] (25/26 March 1941). The {{lang|it|Motoscafo trasporto lento}} (MTL, slow transport motorboat) was a wooden-hulled boat {{cvt|8.5|m|order=flip}} long by {{cvt|2.9|m|order=flip}} wide, to carry {{lang|it|maiali}} close to the target. The MTL had a range of only {{cvt|60|nmi}} cruising at {{cvt|5|kn}}, few were built and they were rarely used. Surface transport gave way to submarines; early in 1940 the {{ship|Italian submarine|Ametista||up=yes}} began tests as a {{lang|it|maiale}} transport. The maximum depth of submersion was only {{cvt|30|m|order=flip}}; {{ship|Italian submarine|Iride||up=yes}} was converted in July 1940 but was sunk on 21 August. {{ship|Italian submarine|Gondar||up=yes}} was sunk on 30 September, even though the three {{lang|it|maiali}} cylinders could be flooded, allowing the boat to reach a depth of {{cvt|295|ft}}.{{sfn|Crociani|Battistelli|2013|pp=13–14}}

==== {{lang|it|Motoscafo turismo}} (MT/MTM) ====
[[File:4B-10Exercise.jpg|left|thumb|{{center|MTM of {{lang|it|Decima MAS}}}}]]
The first {{lang|it|Motoscafo turismo}} (MT) became known as {{lang|it|barchini}} (little boats) were built in late 1938, six MT being delivered in early 1939. An improved version {{lang|it|MT Modificato}} (MTM) tested in November 1940, was {{cvt|6.1|m|order=flip}} long. Both types carried an explosive charge of {{cvt|300|–|330|kg|order=flip}} in the bows at up to {{cvt|31|kn}}. 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 {{lang|it|MT Ridotto}} was built with a height of {{cvt|1.14|m|order=flip}} to fit inside the deck cylinders of submarines with the same explosive charge but they were never used in this manner.{{sfn|Crociani|Battistelli|2013|p=15}}{{clear}}

==== {{lang|it|MT Siluranti}} (MTS) ====
[[File:MAScamo.jpg|thumb|{{center|[[MAS (motorboat)|Motoscafo armato silurante]]}}]]
The {{lang|it|MT Siluranti}} (MTS, torpedo motorboat), was a small boat carrying one or two modified {{cvt|450|mm}} torpedoes, the MTS being more manoeuvrable than the usual {{lang|it|[[MAS (motorboat)|Motoscafo armato silurante]]}}. The first MTS, of early 1941, could reach {{cvt|28|kn}} with a range of {{cvt|158|km|nmi|order=flip}}. The {{lang|it|Decima MAS}} was assisted by {{lang|it|Regia Marina}}  MAS boats, which by June 1940, had fifty Class 500 MAS and another 25 in 1941 in four versions. The Class 500 was {{cvt|18.7|m|order=flip}} long by {{cvt|4.7|m|order=flip}} wide at the beam, with a  displacement of {{cvt|22|–|29.4|t|order=flip}}. The MAS had a crew of 9 to 13 men and had two {{cvt|450|mm|order=flip}} torpedoes, 6–10 depth charges and a {{cvt|13.2|mm}} heavy machine-gun (replaced in 1941 with a Breda 20 mm cannon). The MAS could move at {{cvt|44|kn}} and had a range of {{cvt|645|–|1600|km|nmi|order=flip}}.

=== List of {{lang|it|decima MAS equipment}} ===
{| class="wikitable sortable"
|+{{lang|it|Decima MAS}} equipment{{sfn|Crociani|Battistelli|2013|loc=Endpaper}}
! width="150px" scope="col" |Name
! width="30px" scope="col" |[[Acronym]]
! width="200px" scope="col" |English translation
!Notes
|-
| align="left" |{{lang|it|Uomini Gamma}}
| align="center" |—
| align="left" |Gamma Men
| align="left" |[[Frogmen]] sabotage specialists
|-
| align="left" |{{lang|it|[[MAS (motorboat)|Motoscafo armato silurante]]}}
| align="center" |MAS
| align="left" |Armed torpedo motorboat
| align="left" |Similar to a British [[Motor torpedo boat]] (MTB)
|-
| align="left" |{{lang|it|[[MT explosive motorboat|Motoscafo turismo]]}}
| align="center" |MT
| align="left" |Leisure motorboat
| align="left" |Explosive assault boat, 12 built
|-
| align="left" |{{lang|it|Motoscafo trasporto lento}}
| align="center" |MTL
| align="left" |Slow transport motorboat
| align="left" |Known as {{lang|it|Barchini}} (little boats)
|-
| align="left" |{{lang|it|Motoscafo turismo modificato}}
| align="center" |MTM
| align="left" |Improved explosive assault motorboat
| align="left" |Forty built
|-
| align="left" |{{lang|it|Motoscafo turismo ridotto}}
| align="center" |MTR
| align="left" |Small assault motorboat
| align="left" |
|-
| align="left" |{{lang|it|Motoscafo turismo silurante}}
| align="center" |MTS
| align="left" |Torpedo motorboat
| align="left" |
|-
| align="left" |{{lang|it|MTS modificato}}
| align="center" |MTSM
| align="left" |Improved torpedo motorboat
| align="left" |
|-
| align="left" |{{lang|it|Siluro lenta corsa}}
| align="center" |SLC
| align="left" |Slow human torpedo
| align="left" |
|-
|}

== 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 sank the World War I-era [[Royal Navy]] battleships {{HMS|Valiant|1914|6}} and {{HMS|Queen Elizabeth|1913|6}} (both of which, after months of work, were refloated and returned to action), wrecked the [[heavy cruiser]] {{HMS|York|90|6}} and the [[destroyer]] {{HMS|Eridge|L68|6}}, damaged the destroyer {{HMS|Jervis|F00|6}} and sank or damaged 20 [[merchant ship]]s, including supply ships and tankers. During the course of the war, the Decima MAS was awarded the [[Gold Medal of Military Valor|Golden Medal of Military Valour]] and individual members were awarded a total of 29 [[Gold Medal of Military Valor|Golden Medals of Military Valour]],{{efn|The highest number awarded to personnel serving in any single unit of the Italian armed forces.}} 104 [[Silver Medal of Military Valor|Silver Medals of Military Valour]] and 33 [[Bronze Medal of Military Valor|Bronze Medals of Military Valour]].

=== 1940 ===
[[File:Maiale at gosport.jpg|thumb|Italian ''Maiale'' human torpedo "[[Siluro San Bartolomeo]]" 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 {{ship|Italian submarine|Iride||2}} (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 bomber]]s.  Teseo Tesei survived the attack, but casualties among the submarine crew were heavy.<ref>{{Cite web|url=http://www.regiamarina.net/xa_mas/actions_us.htm|archiveurl=https://web.archive.org/web/20090417014941/http://www.regiamarina.net/xa_mas/actions_us.htm|title=Principal Operations of the 10th Light Flotilla|archivedate=17 April 2009|website=www.regiamarina.net}}</ref>
* 21 September 1940: The Italian submarine ''[[Italian submarine Gondar|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 {{ship|Italian submarine|Sciré|1938|2}}, 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 ''[[HMS Barham (04)|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 ===
[[File:HMSYorkDamaged41941.jpg|thumb|Wreck of HMS ''York'' inspected by the crew of the Italian [[Spica-class torpedo boat|torpedo boat ''Sirio'']], moored alongside]]
* 25 March 1941: The Italian destroyers {{ship|Italian destroyer|Francesco Crispi||2}} and {{ship|Italian destroyer|Quintino Sella||2}} departed [[Leros]] island in the [[Aegean Sea|Aegean]] at night, each carrying 3 small (2-ton) [[MT explosive motorboat|''Motoscafo da Turismo'']] motor assault boats of the Decima MAS.  Each MT (nicknamed ''barchini'' or "little boats") carried a 300&nbsp;kg (660&nbsp;lb) explosive charge in its [[Bow (ship)|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]] {{HMS|York|90|6}}, 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 [[Battle of Crete|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 [[Cadiz]], [[Spain]] it secretly embarked eight Decima MAS crewmen. At Gibraltar, they found no warships because {{HMS|Renown|1916|2}}, {{HMS|Ark Royal|91|2}}, and {{HMS|Sheffield|C24|2}} had been ordered to the [[Atlantic]] to hunt the German battleship {{ship|German battleship|Bismarck||2}}. 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.<ref name="ReferenceA">pp. 6–11, issue 39, Historical Diving Times</ref>
[[File:Слима.jpg|thumb|The remains of [[St. Elmo Bridge]] in [[Valletta]], which was destroyed in the attack of 26 July 1941]]
* 26 July 1941: Two ''Maiale'' and ten MAS boats (including six ''barchini'') [[Battle of Grand Harbour|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]] {{ill|Alcide Pedretti|it}} 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.<ref name="ReferenceA" />  All 6 MTMs, both SLCs and two MAS (MAS 451 and MAS 452<ref>''Our Name Wasn't Written – a Malta Memoir'', [[Caroline Vernon]], Canberra, 1992, p. 36 {{ISBN|0-646-07198-X}}</ref>) 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,<ref>{{cite web |url=http://www.marina.difesa.it/storia/movm/Parte06/bio06/MOVM6056b.asp |archive-url=https://archive.today/20070621072644/http://www.marina.difesa.it/storia/movm/Parte06/bio06/MOVM6056b.asp |url-status=dead |archive-date=21 June 2007 |access-date=17 September 2009 |title=Ernesto FORZA – Capitano di Fregata }}</ref> and Borghese became leader of the sub-surface weapons group.<ref>Kemp p. 51</ref>
* 10 September 1941: The ''Sciré'' departed La Spezia carrying three human torpedoes. At Cadiz, Spain, it secretly embarked eight crewmen for them. At Gibraltar, the torpedoes sank three ships: the [[Tanker (ship)|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 [[destroyer]]s pass. After many difficulties, de la Penne and his crewmate Emilio Bianchi successfully attached a limpet mine under {{HMS|Valiant|1914|6}}, 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 ''Valiant''{{'}}s 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 sank ''Valiant'', the battleship {{HMS|Queen Elizabeth|1913|2}}, and the Norwegian tanker ''Sagona'', and badly damaged the destroyer {{HMS|Jervis|F00|6}}. The two battleships sank in only a few feet of water and were subsequently re-floated and repaired, being 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 [[Italian auxiliary ship Olterra|''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 (1938)|Italian submarine ''Scirè'']] was sunk by [[HMS Islay|HMS ''Islay'']] while attempting to attack the port of [[Haifa]] in British [[Mandate Palestine|Palestine]]. She had 11 frogmen on board.<ref>{{cite web|url=http://www.iantdexpeditions.com/notizie/2008/scireen.pdf |title=Scire' 2008 : Archaeological Survey |publisher=Iantdexpeditions.com |access-date=2015-08-18}}</ref>
* 29 August 1942: Off [[RAF El Daba|El Daba]], Egypt. The {{sclass2|Hunt|destroyer}} {{HMS|Eridge|L68|6}} was torpedoed at close range by an [[MTSM motor torpedo boat|MTSM]], a torpedo-carrying version of the [[MT explosive motor boat|MTM]]. Six of her crew were lost.  {{HMS|Eridge|L68|6}} was towed to Alexandria, but soon after was declared a "constructive total loss", and was scrapped in 1946.<ref>{{cite web|url=http://www.naval-history.net/xGM-Chrono-10DE-Eridge.htm |title=HMS Eridge, escort destroyer |publisher=Naval-history.net |access-date=2015-08-18}}</ref>
* 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 {{HMS|Nelson|28|2}}, {{HMS|Formidable|R67|2}}, and {{HMS|Furious|47|2}} 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 [[swimfin]]s 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|''Liberty'' ship]]. All returned safely to the ''Olterra''.
[[File:OlterraVictim-2.jpg|thumb|This drawing shows the Norwegian tanker ''Thorshøvdi'', broken in two by [[human torpedo]]es launched from the Italian base-ship ''Olterra'', August 1943]]
* May 1943: Borghese becomes unit commander when Forza returned to sea<ref>Kemp p. 57</ref>
* 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]].<ref name=Jorgensen93>Jørgensen 2005, p. 93.</ref>
* 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]].<ref name=Jorgensen93/>

===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===
{| class="wikitable"
|-
! scope="col" width="120px"  |Date
! scope="col" width="80px"  |Place
!  |Notes
|-
|26 March 1941
|[[Suda Bay]]
|Cruiser {{HMS|York|90|6}} (8,250 t [[standard displacement]]){{Efn|Disabled by two MT explosive speedboats piloted by Lt.(jg) Angelo Cabrini and SCPO Tullio Tedeschi. Abandoned and never repaired.}} Tanker ''Pericles'' (8,234 t){{efn|Sunk by an MT explosive speedboat piloted by PO2 Lino Beccati.}}
|-
|19 September 1941
|[[Gibraltar]]
|Tanker ''Denby Dale'' (8,145 t){{efn|Sunk by an explosive charge positioned by the human torpedo piloted by Lt.(jg) Licio Visintini and PO1 Giovanni Magro.}} Tanker ''Fiona Shell'' (2,445 t){{efn|Disabled by an explosive charge positioned by the human torpedo piloted by Lt.(jg) Amedeo Vesco and PO1 Antonio Zozzoli. Later repaired and returned to service.}} Motorship ''Durham'' (10,900 t){{Efn|Damaged by an explosive charge positioned by the human torpedo piloted by Lt.(jg) Decio Catalano and PO1 Giuseppe Giannoni. Later repaired and returned to service.}}
|-
|19 December 1941
|[[Alexandria]]
|Battleship {{HMS|Queen Elizabeth|1913|6}} (30,600 t){{efn|Sunk in shallow water by an explosive charge positioned by the human torpedo piloted by Lt.(jg) Antonio Marceglia and PO1 Spartaco Schergat. Later raised from the bottom and repaired.}} Battleship {{HMS|Valiant|1914|6}} (30,600 t){{efn|Sunk in shallow water by an explosive charge positioned by the human torpedo piloted by Lt.(jg) Luigi Durand De La Penne and MCPO Emilio Bianchi. Later raised from the bottom and repaired.}} Tanker ''Sagona'' (7,554 t){{efn|Damaged by an explosive charge positioned by the human torpedo piloted by Lt.(jg) Vittorio Martellotta and PO1 Mario Marino. Later repaired and returned to service.}} Destroyer {{HMS|Jervis||6}} (1,690 t){{efn|Damaged by an explosive charge positioned by the human torpedo piloted by Lt.(jg) Vittorio Martellotta and PO1 Mario Marino. Repaired and returned to service.}}
|-
|13 June 1942
|[[Sebastopol]]
|Military transport (USSR){{efn|Damaged by MTSM 210 torpedo speedboat piloted by Lt.(jg) Aldo Massarini and PO1 Eliodoro Grillo. Later sunk by German aircraft while being towed back to port.}}
|-
|14 July 1942
|[[Gibraltar]]
|Steamship ''Meta'' (1,575 t){{efn|All damaged by limpet mines positioned by assault frogmen (Lt.(jg) Agostino Straulino and Giorgio Baucier, SCPO Alfredo Schiavoni, PO1 Alessandro Bianchini, E4 Giovanni Lucchetti, Carlo Del Valle, Giuseppe Ferodi, Vago Giari and Evideo Boscolo, E3 Bruno Di Lorenzo, Rodolfo Lugano and Carlo Bucovaz).}} [[List of Empire ships (Si–Sy)#Empire Snipe|SS ''Empire Snipe'']] (2,497 t){{efn|Repaired and returned to service in October 1942.}} Steamship ''Shuma'' (1,494 t) Steamship ''Baron Douglas'' (3,899 t)
|-
|29 August 1942
|El Daba
|Destroyer {{HMS|Eridge|L68|6}} (1,050 t){{efn|Disabled by MTSM 210 torpedo speedboat piloted by Lt.(jg) Piero Carminati and E4 Cesare Sani, never repaired.}}
|-
|15 September 1942
|[[Gibraltar]]
|Steamship ''Raven's Point'' (1,787 t){{efn|Sunk by limpet mines positioned by assault frogman E3 Bruno Di Lorenzo.}}
|-
|12 December 1942
|[[Algiers]]
|Steamship ''Ocean Vanquisher'' (7,174 t){{efn|Sunk during a combined raid of human torpedoes (Lt.(jg) Giulio Arena and E4 Ferdinando Cocchi; Ens. Giorgio Reggioli and E4 Colombo Pamolli) and assault frogmen (Lt.(jg) Agostino Morello, PO1 Oreste Botti, E4 Giuseppe Ferodi and Evideo Boscolo, Sgt. (Army) Luigi Rolfini and Alberto Evangelisti).}} Steamship ''Berta'' (1,493 t){{efn|Sunk}} Steamship ''Armattan'' (6,587 t)<ref name="DAM">Damaged</ref> Tanker ''[[List of Empire ships (Ca–Cl)#Empire Centaur|Empire Centaur]]'' (7,041 t) (repaired)<ref name="DAM"/>USN Military Transport ''N.59''<ref name="DAM"/>
|-
|8 May 1943
|[[Gibraltar]]
|Steamship ''Pat Harrison'' (U.S.) (7,191 t){{efn|All disabled by explosive charges positioned by three human torpedoes (Lt.Ernesto Notari and E4 Ario Lazzari; Lt.(jg) Camillo Tadini and E4 Salvatore Mattera; Lt.(jg) Vittorio Cella and E4 Eusebio Montalenti.}} Steamship ''Mahsud'' (7,540 t) Steamship ''Camerata'' (4875 t)
|-
|30 June 1943
|[[İskenderun]]
|Motorship ''Orion'' (Greek) (7,000 t){{efn| name="MOFer"|Sunk by limpet mines positioned by assault frogman Lt. ([[Blackshirts]]) Luigi Ferraro.}}
|-
|9 July 1943
|[[Mersin]]
|Motorship ''Kaituna'' (4914 t){{efn|name="MOFer"}}
|-
|1 August 1943
|[[İskenderun]]
|Motorship ''Fernplant'' (Norwegian) (7000 t){{efn|name="MOFer"}}
|-
|4 August 1943
|[[Gibraltar]]
|Steamship ''Harrison Gray Otis'' (U.S.) (7,176 t){{efn|Sunk by an explosive charge positioned by the human torpedo piloted by Lt. Ernesto Notari and E4 Andrea Gianoli.}} Steamship ''Stanridge'' (5,975 t){{efn|Sunk by an explosive charge positioned by the human torpedo piloted by Lt.(jg) Camillo Tadini and E4 Salvatore Matera.}} Tanker ''Thorshøvdi'' (Norwegian) (9,944 t){{efn|Sunk by an explosive charge positioned by the human torpedo piloted by Lt.(jg) Vittorio Cella and E4 Eusebio Montalenti.}}
|}

==Successor units==
[[File:Bundesarchiv Bild 101I-311-0926-06, Italien, italienische Soldaten.jpg|thumb|[[Military ranks of the Italian Social Republic|Guardiamarina]] ([[Ensign (rank)|Ensign]]) of the Barbarigo Battalion standing in viale Carso near piazza Bainsizza, in Rome, during a review parade by [[General der Luftwaffe]] [[Kurt Mälzer]] before being sent to face the [[Battle of Anzio|Allied beachhead at Anzio-Nettuno]], March 1944.]]
Following the [[armistice]] of Italy on 8 September 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 [[prisoner of war|POW camps]].
The new unit was named ''Mariassalto'', but continued to be an elite naval force mounting special operations at sea.

In the German-occupied north of Italy. Mussolini set up the
[[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 headquarters 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 naval unit, it gained a reputation as a savage pro-fascist, anti-communist, anti-resistance force in land campaigns alongside the German forces, under the command of [[SS]] General [[Karl Wolff]].

===Mariassalto===
{{Infobox military unit
| unit_name                     = Mariassalto
| image                         = 
| caption                       = 
| start_date                    = October 1943
| end_date                      = 26 April 1945
| country                       = {{flag|Kingdom of Italy}}
| branch                        = [[Italian Co-Belligerent Navy]]
| type                          = Naval commandos
| role                          = [[Human torpedo]]<br>[[Raid (military)|Raiding]]<br>[[Sabotage]]
| size                          = 
| command_structure             = 
| garrison                      = 
| garrison_label                = 
| nickname                      = 
| patron                        = 
| motto                         = 
| colors                        = 
| colors_label                  = 
| march                         = 
| mascot                        = 
| equipment                     = [[Human torpedo#United Kingdom|Chariot]]
| equipment_label               = Equipment
| battles                       = Raid on Genoa<br />Raid on La Spezia
| anniversaries                 = 
| decorations                   = 
| battle_honours                = 
| disbanded                     = <!-- Commanders -->
| commander1                    = 
| commander1_label              = 
| commander2                    = 
| commander2_label              = 
| commander3                    = 
| commander3_label              = 
| notable_commanders            = Ernesto Forza
<!-- Insignia -->| identification_symbol         = 
| identification_symbol_label   = 
| identification_symbol_2       = 
| identification_symbol_2_label = 
| identification_symbol_3       = 
| identification_symbol_3_label = 
| identification_symbol_4       = 
| identification_symbol_4_label = 
}}

The ''Mariassalto'' was set up at [[Taranto]] alongside the [[Royal Navy|British]] [[British commando frogmen|frogman force]] in the Mediterranean. Forza was pleased to demonstrate Italian expertise in this area to the British,<ref name="Kemp p61">Kemp p. 61</ref> and the group was also keen to be in action, though if they were caught they would almost certainly have been shot.<ref name="Kemp p63">Kemp p. 63</ref>

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 ''[[Italian cruiser Bolzano|Bolzano]]'' and ''[[Italian cruiser Gorizia|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 chariots would attack the cruisers whilst ''Mariassalto's'' Gamma Frogmen would attack U-boats penned in the harbour.
On 2 June 1944 the Italian destroyer {{ship|Italian destroyer|Grecale||2}} 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, linking with partisan groups on land.<ref name="Kemp p63"/>

In April 1945 a final mission, Operation Toast, was planned.<ref>[http://parridigit.istitutoparri.eu/public/multimediale/1/.../Special_force_2.pd]{{dead link|date=August 2015}}</ref> This was aimed at sinking the newly converted shipping liner now the aircraft carrier ''[[Italian aircraft carrier Aquila|Aquila]]'', just completed in Genoa.
For this ''Mariassalto'' men would make use of two British chariots, as they had none of their own SLCs available.
On 18 April 1945 the destroyer {{ship|Italian destroyer|Legionario||2}}, carrying two high-speed motorboats equipped with chariots sailed from Venice for Genoa led by Captain Chavasse SOE and Forza. Both chariots were deployed and succeeded in penetrating the defences but found the hull of ''Aquila'' so encrusted with barnacles and seaweed the limpet mines could not be attached to it. The frogmen had to lay the charges on the seafloor of the outer harbour mole and when the charge exploded as planned the ship remained afloat in spite of the attack. All of the frogmen escaped safely. The German commander never put his extensive demolition plans for Genoa into action and thus Aquila was never sunk as a blockade to the harbour.

===Decima MAS (RSI)===
{{Infobox military unit
| unit_name                     = Decima Flottiglia MAS
| image                         = Logodcima.jpg
| caption                       = 
| start_date                    = September 1943
| end_date                      = 26 April 1945
| country                       = {{flag|Italian Social Republic}}
| branch                        = Navy
| type                          = [[Marines]]<br />Naval commandos
| role                          = [[Amphibious warfare]]<br />Anti-partisan<br />[[Close-quarters combat]]<br />[[Counter-insurgency]]<br />[[Counterintelligence]]<br />[[Direct action (military)|Direct action]]<br />[[Raid (military)|Raiding]]<br />[[Reconnaissance]]<br />[[Sabotage]]
| size                          = 
| command_structure             = 
| garrison                      = 
| garrison_label                = 
| nickname                      = Xª MAS
| patron                        = 
| motto                         = [[Memento Audere Semper]] (Remember to dare always)
| colors                        = 
| colors_label                  = 
| march                         = 
| mascot                        = 
| equipment                     = 
| equipment_label               = 
| battles                       = 
| anniversaries                 = 
| decorations                   = 
| battle_honours                = 
| disbanded                     = <!-- Commanders -->
| commander1                    = 
| commander1_label              = 
| commander2                    = 
| commander2_label              = 
| commander3                    = 
| commander3_label              = 
| notable_commanders            = [[Junio Valerio Borghese]]
<!-- Insignia -->| identification_symbol         = 
| identification_symbol_label   = 
| identification_symbol_2       = 
| identification_symbol_2_label = 
| identification_symbol_3       = 
| identification_symbol_3_label = 
| identification_symbol_4       = 
| identification_symbol_4_label = 
}}
[[File:Junio Valerio Borghese and Umberto Bardelli.jpg|thumb|[[Junio Valerio Borghese]] (right) and [[Umberto Bardelli]] of the Decima MAS.]]
Some Xª MAS men who were in German-occupied Italy remained part of the [[Axis Powers|Axis]] forces, joining the [[Italian Social Republic]] under the command of Captain Borghese. His reputation and that of the Xª MAS 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.<ref>{{cite web|url=http://digilander.libero.it/ladecimamas/fronte%20orientale.htm |title=Il Mito della difesa del fronte orientale |publisher=Digilander.libero.it |access-date=2015-08-18}}</ref>

==== Ideology ====
The main themes in the Xª MAS's ideology became "[[honour]]" in defending Italy from the "[[betrayal]]" of the armistice with the Allies and a call to defend the territorial integrity of Italy against the Allies.
The corps had its own weekly magazine, ''L'orizzonte'' ("The Horizon"), in which authors such as [[Giovanni Preziosi]] wrote vehemently anti-Semitic articles about [[Jew]]ish [[conspiracy theory|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.<ref>{{cite web|url=http://digilander.libero.it/ladecimamas/orizzonte.htm |title=Junio Valerio Borghese |publisher=Digilander.libero.it |access-date=2015-08-18}}</ref>

==== Hymn ====
{{Verse translation
 | lang       = it
 | italicsoff =
 | rtl1       =
|Quando pareva vinta Roma antica,
sorse l'invitta decima legione;
vinse sul campo il barbaro nemico,
Roma riebbe pace con onore;
quando l'ignobil 8 di settembre,
abbandonò la patria il traditore,
sorse dal mar la decima flottiglia,
che prese l'armi al grido "per l'onore!".

Decima flottiglia nostra,
che beffasti l'inghilterra,
vittoriosa ad Alessandria,
Malta, Suda e Gibilterra;
vittoriosa già sul mare,
ora pure sulla terra,
vincerai!

Navi d'Italia che ci foste tolte,
non in battaglia, ma col tradimento,
nostri fratelli prigionieri o morti,
noi vi facciamo questo giuramento:
noi vi giuriamo che ritorneremo,
là dove Dio volle il tricolore;
noi vi giuriamo che combatteremo,
fin quando avremo pace con onore.

Decima flottiglia nostra,
che beffasti l'inghilterra,
vittoriosa ad Alessandria,
Malta, Algeri e Gibilterra;
vittoriosa già sul mare,
ora pure sulla terra,
vincerai!
|When ancient Rome seemed defeated,
arose the invincible [[Legio X Equestris|Tenth Legion]];
On the field she defeated the barbarous enemy,
Rome regained peace with honor;
when, [in] the ignoble September Eight,
the traitor abandoned the Fatherland,
arose from the sea the Tenth Flotilla
who took up arms with the cry "for the honor".

Our [glorious] Tenth Fleet,
that humiliated England,
victorious at [[Alexandria]],
[[Malta]], [[Souda]] and [[Gibraltar]];
already victorious over the sea,
now as well on earth,
you will win!

[For] Ships of Italy that were wiped away,
not in battle but by treachery,
our fellows prisoners or dead,
we make this pledge for you:
We swear that we will return later
where God wanted the Tricolour;
We swear that we will fight,
till we'll have peace with honor.

Our [glorious] tenth Flotilla,
that humiliated England,
victorious at Alexandria,
Malta, [[Algiers]] and Gibraltar;
already victorious over the sea,
now as well on earth,
you will win!}}

==== Relations with the RSI ====
[[File:Bundesarchiv Bild 101I-311-0926-04, Italien, italienische Soldaten.jpg|thumb|Marines of the ''Decima'', in 1944]]
Relationships with the Italian Social Republic were not easy. On 14 January 1944 [[Benito Mussolini]] arrested Borghese while receiving him in [[Gargnano]], 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.<ref>{{cite web|url=http://digilander.libero.it/ladecimamas/vivarelli.htm |title=Junio Valerio Borghese |publisher=Digilander.libero.it |access-date=2015-08-18}}</ref>

==== 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.<ref name="Kemp p61"/>
In November 1944 four frogmen (Malacarne, Sorgetti, Bertoncin, Pavone), who had stayed under [[Nazi Germany|German]] command, were delivered by fast motorboat and swam into [[Livorno]] harbor to set up a secret sabotage base, but were captured.<ref>pp. 16–20, issue 41, ''The Historical Diving Times'', {{ISSN|1368-0390}}</ref>

==== Anti-partisan actions ====
[[File:FerruccioNazionale.jpg|thumb|Ferruccio Nazionale, [[Italian resistance movement|Italian partisan]] hanged by the Xª MAS in [[Ivrea]]. The sign says: "He attempted to shoot the ''Decima''"]]
The Decima was mostly employed in anti-partisan actions on land, rather than against the Allies at sea. Their actions were mostly reprisals following the massacre of soldiers of "Decima" by partisans– see Bardelli's homicide. Their anti-partisan actions usually took place in small villages, where the partisans were stronger.
* [[Forno (Massa)|Forno]] 68 persons, civilians and some partisans, were killed by SS men and Xª MAS forces.<ref>{{cite web|url=http://static.repubblica.it/iltirreno/PDF/Sant%27Anna/BardineSanTerenzo.pdf|title=static.repubblica.it – Documento Tribunale Militare di La Spezia |access-date=1 September 2012 |language=it }}</ref><ref>{{cite web|url=http://digilander.libero.it/ladecimamas/pagina3.htm |title=Junio Valerio Borghese |publisher=Digilander.libero.it |access-date=2015-08-18}}</ref>
* [[Guadine]] Random violence to terrorize a population believed to be supporting the rebels, almost complete destruction of the village by fire.<ref>{{cite web|url=http://digilander.libero.it/ladecimamas/stragi2.htm |title=Stragi Guadine |publisher=Digilander.libero.it |access-date=2015-08-18}}</ref>
* [[Borgo Ticino]] Together with the SS, murdered 12 civilians, pillage and destruction of the village by fire because three German soldiers had been wounded by partisans.<ref>{{cite web|url=http://digilander.libero.it/ladecimamas/stragi3.htm |title=Stragi eccidio di borgo ticino |publisher=Digilander.libero.it |access-date=2015-08-18}}</ref>
* [[Castelletto Ticino]] To give a demonstration of firmness against crime, an Xª MAS officer had five petty criminals publicly shot, in front of a large crowd.<ref>{{cite web|url=http://digilander.libero.it/ladecimamas/stragi4.htm |title=Stragi Castelletto Ticino |publisher=Digilander.libero.it |access-date=2015-08-18}}</ref>
* [[Crocetta del Montello]]: Episodes of [[torture]] with [[whip]]s and [[gasoline]] and [[summary execution]]s of partisans.<ref>{{cite web|url=http://digilander.libero.it/ladecimamas/stragi5.htm |title=L'eccidio di Crocetta del Montello (TV) |publisher=Digilander.libero.it |access-date=2015-08-18}}</ref>

====Defense of Italian national borders====
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 [[Josip Broz Tito]]'s [[Partisans (Yugoslavia)|partisans]] who marched into [[Istria]] and [[Venezia Giulia]].

==== Demobilization ====
On 26 April 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. Borghese was tried and convicted of war crimes, and sentenced to 12 years imprisonment, but was 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 X<sup>a</sup> 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==
{{Further|Italian commando frogmen}}
In 2006 the admiralty of the Italian republic recognized the Xth M.A.S. RSI veterans as combatants of WWII and gave the association the battle flag.

Counter-operations against Italian frogmen by British frogmen in Gibraltar was the subject of a 1958 British film [[The Silent Enemy (1958 film)|''The Silent Enemy'']] based on the exploits of the team of [[Lionel Crabb]].

Today the [[Comando Raggruppamento Subacquei e Incursori Teseo Tesei]] is the frogman corp currently serving the [[Italian Republic]].

==In popular culture==
* The Decima MAS' Gibraltar operations are depicted in the 1952 Italian film ''I sette dell'Orsa maggiore'' and the 1958 British film  [[The Silent Enemy (1958 film)|''The Silent Enemy'']].
* The Uniforms of the Decima Flottiglia MAS are used by the collaborationists in the film ''[[Salò o le 120 giornate di Sodoma]]''.
* The [[Raid on Alexandria (1941)|Raid on Alexandria]] in 1941 is depicted in the 1962 British film [[The Valiant (1962 film)|''The Valiant'']].
* In the Italian film ''[[My Brother is an Only Child]]'', set in the 1960s, a young Communist refers to the Decima Mas, and their "dungeon" on [[Via Tasso]].
Prince Valerio Borghese escaped capital punishment after the war (thanks to [[James Jesus Angleton]] of the CIA) in the cold war context and remained an active neo-fascist activist: He attempted a failed fascist coup in the early 1970s (the infamous [[golpe Borghese]]).
The Golpe Borghese and its leader are spoofed in a film by [[Mario Monicelli]] called ''Vogliamo i Colonelli'' (''[[We Want the Colonels|We want the Colonels]]'') where Borghese part is played by Italian actor [[Ugo Tognazzi]] impersonating an ultra right-wing parliament representative called Tritoni (Triton or Newt). One of the best scenes features a boisterous and crazy assault diver and parachute Commando frogman called Barbacane (Giuseppe Maffioli).

==See also==
{{Portal|Underwater diving}}
* {{annotated link|Italian auxiliary ship Olterra}}
* {{annotated link|Brandenburgers}}
* {{annotated link|Fukuryu}}
* {{annotated link|Comando Raggruppamento Subacquei e Incursori Teseo Tesei}}, the [[COMSUBIN]]
* {{annotated link|MAS (motorboat)}}
* {{annotated link|Military history of Gibraltar during World War II}}

==Notes==
{{notelist|1}}

==Citations==
{{Reflist|30em}}

==References==
* {{cite journal|last1=Caruana|first1=J.|year=1991 |title=Decima Flotilla Decimated|journal=Warship International|volume=XXVIII |issue=2 |pages=178–186 |issn=0043-0374}}
* {{cite book |last1=Crociani |first1=P. |last2=Battistelli |first2=P. P. |series=Elite (No. 191) |title=Italian Navy & Air Force Elite Units & Special Forces1940–45 |year=2013 |publisher=Osprey |location=Oxford |edition=ePub |isbn=978-1-78096-372-3}}
* {{cite journal|last=Jørgensen|first=Sven Erik|title=The First Frogmen 2: Naval Operations with the SLC|journal=X-Ray Mag: International Dive Magazine|publisher=AquaScope Media ApS|location=Copenhagen|url=http://www.xray-mag.com/pdfs/articles/Feature_FirstFrogmen_09.pdf|volume=8|pages=85–93|issn=1901-9238}}

==Further reading==
* "''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==
* [http://www.regiamarina.net/detail_text.asp?nid=26&lid=1 The origin of the Xa Flottiglia MAS]
* [http://digilander.libero.it/ladecimamas/ La Decima MAS] {{in lang|it}}
* [https://web.archive.org/web/20131022161652/http://www.rolexwallpaper.com/wp-content/uploads/2013/09/Italian-Navy-Frogmen-Rebreather-800x675.jpg] Image of Italian wartime frogman with rebreather whose breathing tube and [[fullface mask]] resemble an old type of [[gasmask]], but with the mask's blowoff valve blanked off.

{{Underwater diving|prodiv}}

{{DEFAULTSORT:Decima Flottiglia Mas}}
[[Category:Military units and formations of Italy in World War II]]
[[Category:Italian special forces of World War II]]
[[Category:MAS fleet]]
[[Category:Military units and formations established in 1941]]
[[Category:Military units and formations disestablished in 1943]]
[[Category:Military units and formations established in 1943]]
[[Category:Military units and formations disestablished in 1945]]
[[Category:Gibraltar in World War II]]
[[Category:Frogman operations]]
[[Category:1941 establishments in Italy]]
[[Category:1943 disestablishments in Italy]]
[[Category:1943 establishments in Italy]]
[[Category:1945 disestablishments in Italy]]
[[Category:Naval special forces units and formations]]
[[Category:Disbanded marine forces]]
[[Category:Italian Marines]]