Decima Flottiglia MAS 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 boat s 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 Sinking of HMS York ) , manned torpedo es ( the Raid on Alexandria ) and " Gamma " Frogmen ( against ) . During the campaign Decima MAS took part in more than a dozen operations which sank or damaged five 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 . 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 and the freighter " Wien " using limpet mine s . 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 swimfin s , diving mask s and snorkel s . In the 1930s Italian sport spearfishermen began using industrial or submarine - escape oxygen rebreather s , 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 Major s 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 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 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 and ( both of which , after months of work , were refloated and returned to action ) , 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 . 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 " 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 Army ( " Wehrmacht Heer " ) , under the command of SS General Karl Wolff . Mariassalto . 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 , and the group was also keen to be in action , though if they were caught they would almost certainly have been shot . 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 . 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 Gerolamo 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 . Decima MAS ( RSI ) . 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 . 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 . Ideology . 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 . The magazine had problems in its distribution , as it was thought that Borghese ' s popularity among the Fascist hardliners might reduce Mussolini ' s influence . Hymn . ( literally ) < br > < poem > « 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 ! ! ! » < / poem > < br > < poem > « When ancient Rome seemed defeated , arose the invincible 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 Motherland , 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 ! < / poem > Relations with the RSI . Relationships with the Italian Social Republic were not easy . On January 14 , 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 . 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 . 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 . Anti - partisan actions . The Decima was mostly employed 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 : 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 who were trying to liberate Istria and Venezia Giulia . Demobilization . 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 . 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 . After 1945 . See 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 " based on the exploits of the team of Lionel Crabb .