Decima Flottiglia MAS

The plan outlined the use of six small, lightweight, and high-speed motorboats (capable of 40 knots), each carrying an explosive charge of approximately 300 kilograms of TNT, the warhead of a torpedo. These motorboats would be suspended from six Savoia-Marchetti SM.55 seaplanes, positioned between the twin hulls.

1. On a night with calm seas, the six seaplanes would transport the motorboats to the vicinity of the target naval base, landing approximately 18 kilometres offshore to avoid detection by enemy patrols.
2. Once released, the motorboats would proceed silently towards the enemy base. Upon reaching the harbour entrance, the lead motorboat would ram the obstruction, detonating its explosive charge to create a breach.
3. The remaining motorboats would navigate through the gap, marked by a floating light left by the lead boat and its helmsman. If further obstructions were encountered, the second boat would repeat the process.
4. Once inside the port, the motorboats would accelerate towards anchored vessels, with the helmsman abandoning the craft just before impact, triggering detonation upon collision.
5. The operation could involve additional motorboats (nine to twelve) and be repeated at intervals, exploiting the difficulty of establishing an effective defence in a short period.

The document concludes with the authors, Amedeo Duca d’Aosta, Giorgi, and Margottini, expressing their desire to personally lead the mission if the project were approved. Fate, however, dictated otherwise. Frigate Captain Margottini lost his life commanding the destroyer Artigliere during the night of October 12^th,1940. Captain Giorgi fell in action while commanding the cruiser Fiume during the Battle of Cape Matapan on March 29^th, 1941. Admiral Aimone di Savoia-Aosta did not find rest in Italian waters, and Amedeo Duca d’Aosta died in captivity, laid to rest in Africa after the valiant defence of Amba Alagi.

Engineer Guido Cattaneo and by Comander Mario Giorgini were tasked with the design of the prototypes. They came up with two prototypes, the Motoscafo d’Assalto (M.A.) and the Motoscafo Avio Trasportato (M.A.T.), an airborne prototype. The prototypes were made of wood and canvas with a small, bow-mounted, impact-fused explosive charge.

During the same time period, two naval engineers. Teseo Tesei and Elios Toschi, at the Livorno Accademia Navale each produced a new design for the Torpedine Rossetti. In the late 1920s, Captains Teseo Tesei and Elios Toschi of the Genio Navale, both engineers serving aboard the H-class submarines of the La Spezia Group, begin exploring the concept of a manned submersible weapon. Tesei, having first conceived the idea in 1927 while studying at the Naval Academy before earning his qualifications in naval and mechanical engineering, refines the concept alongside Toschi. Their vision revolves around modifying a 533-millimetre torpedo to carry two operators equipped with self-contained breathing apparatus. This specialised craft, an underwater evolution of the Mignatta, is designed to discreetly deliver an explosive charge to the hulls of enemy warships, targeting vessels at anchor or within heavily guarded harbours.

Raising a Special Naval Unit

These developments made Admiral Cavagnari, the Chief of Staff of the Regia Marina in September 1935 decide to approve the foundation of the 1° Gruppo Sommergibilli. Within this group an independent section is created responsible for the development and operational deployment of assault craft. Commanded by Catalano Gonzaga di Cirella, this section operates from La Spezia, overlooking the first basin of the shipyards. It functions under a veil of secrecy. Underwater operations training initially takes place at Porto Santo Stefano in 1935 before relocating.

This unit becomes the new base for the ideas of Capitano del Genio Navale Teseo Tesei, Capitano del Genio Navale Elios Toschi and Admiral Aimone Savoia D’aosta. For a brief period of time, they had enough funding to optimize their design for what become known as the Siluro a Lenta Corsa (SLC), or Slow Moving Torpedo. The unit also came up with the Motoscafi da Turismo Modificati, or modified tourist motorboat. This boat was based on the prototypes of the Motoscafo d’Assalto (M.A.) a few years earlier. The boat was commonly known as Barchino Esplosivi, explosive boat or simply barchino.

Gruppo Gamma

The Combat Diving branch originates in 1935 with experiments conducted by the 1° Gruppo Sommergibilli in La Spezia. These tests focus on deploying divers equipped with self-contained breathing apparatus from ‘H’ class submarines. The divers, known as bottom-walkers, carry explosive charges on their shoulders to attach to the hulls of anchored enemy vessels.

Diving technology rapidly advances, with operators using autonomous diving suits such as the Belloni hood, Davis, or Dräger rebreathers. These experiments form part of a broader strategy, involving precise submarine navigation inside harbours, slithering along the seabed to avoid detection. Divers also assist submarines in navigating obstructions by either manning the conning tower or sitting at the bow while relaying directions via telephone.

Once within striking distance, typically a few tens of metres from their target, the submarine rests on the seabed, initiating the divers’ exit procedure. These autonomous divers, untethered from the vessel, walk along the bottom to plant explosive charges with clockwork fuses on enemy ships at anchor.

Initial trials confirm the effectiveness of the submarine approach, but the divers struggle with slow movement (approximately 500 metres per hour), poor compass reliability, and limited underwater visibility due to disturbed sediment. Additionally, breathing apparatus performance remains a significant constraint. With the conclusion of the Ethiopian campaign and reduced international tensions, the concept of autonomous divers and bottom-walkers is temporarily abandoned.

Restart of Training

In 1939, training is transferred to the secluded Bocca di Serchio. However, by the end of 1936 the military tension between the Italians and British relaxes a bit and the funding for the 1° Gruppo Sommergibilli is again limited by the Regia Marina. First the Siluro a Lenta Corsa program is put on hold, shortly afterwards followed by Motoscafo d’Assalto program.

It was not until the end of 1938, when international relations starts to worsen up again before the unit received enough funding to start developing both programs again. In September 1938, the unit is renamed to 1° Flottiglia MAS. Capitano di Fregata Paolo Aloisi becomes the new commander of the unit. He is tasked to continue training the unit and prepare for future actions. The unit is headquartered in La Spezia. The unit consolidates three existing MAS squadrons and assumes responsibility for training and equipping personnel for operations. Technical guidance comes from the Permanent Commission for Experiments in War Material (Mariperman) located in La Spezia-San Bartolomeo. The initial cadre of personnel, known as the ‘Aloisi core,’ comprises approximately thirty officers and petty officers.

Diving training also resumes in 1938 and continues throughout the war. A detachment aboard the San Marco and a secondary workshop at Migliarina support training exercises. Training plays a critical role in developing Italy’s assault craft capabilities. Early explosive motorboat pilot training commences in 1938 at the Cottrau battery in La Spezia, where pilots practise evading boom defences and executing timed abandonments.

When Italy resumes its experimental assault craft programme in 1938, diver training shifts primarily toward self-propelled craft operations. However, in the summer of 1940, the Decima Flottiglia Mas establishes a diver school at the Naval Academy in Livorno. Under the leadership of Commander Giulio Belloni and later Tenente di Vascello Eugenio Wolk, the concept of bottom-walking divers is revived and refined.

By this time, diving equipment and techniques have improved significantly. Wolk introduces a new combat specialty, operators known as Guastatori (military engineers or sappers), identified by the letter G, or Gamma in the phonetic alphabet of the time. Unlike earlier bottom-walkers, these assault swimmers operate in a lighter trim, moving primarily on the surface with flippers. They dive only to place their charges, which are specially designed for attacks on merchant ships. Explosive devices such as, bedbugs, and, small trunks, are developed for this purpose.

World War 2

World War 2 broke and Italy entered the war the unit was not fully prepared for their task. In June 1940 when Italy joined Germany in the attack on France the unit had eleven Siluro a Lenta Corsa’s and the submarine Iride for transport of these vessels. Besides that, it had seven Motoscafo Turismo’s for surface assaults.

On February 24^th, 1940, Paolo Aloisi is replaced by Mario Giorgini as commander of the 1° Flottiglia MAS, the special operations unit of the Regia Marina. While Aloisi is recognised for his technical knowledge, Giorgini earns distinction for his organisational skills. The use of the vessels in 1° Flottiglia MAS, comprising five squadrons and a total of twenty MAS, is confirmed, and the role of the assault teams is formally recognised. These teams consist of highly trained divers capable of swimming beneath enemy vessels to attach explosive charges.

The fleet of explosive motorboats, initially considered a “stopgap measure”, is placed under the command of Giorgio Giobbe. These vessels, though initially not deployed in major operations, are based at La Spezia, specifically at the Balipedio Cottrau in Varignano.

At the centre of operations, a Technical-Experimental Department is established under the command of Lieutenant Angelo Belloni, focusing on research and development of new equipment to enhance the efficiency and safety of underwater assault operations. The Gruppo Gamma, commanded by Lieutenant Eugenio Wolk, is one of the primary units trained in these advanced techniques. This group pioneers the use of fins and webbed gloves, significantly improving diver mobility during future missions.

To ensure the success of these raids, the flotilla requires not only offensive capabilities but also advanced navigational instruments such as compasses and depth gauges. These are subject to rigorous study and refinement to ensure precision and reliability in combat conditions.

Giorgini selects submarines as the optimal method for deploying Siluro a Lenta Corsa manned torpedoes near enemy ports. In May 1940, he arranges and supervises the first tests involving submarine transport and release of these torpedoes. The submarine Ametista serves as the Siluro a Lenta Corsa carrier, and the obsolete cruiser Quarto, anchored at La Spezia, acts as the target. Giorgini is joined by Teseo Tesei, Elios Toschi, Junio Valerio Borghese, and Gino Birindelli aboard Ametista. During the exercise, three Siluro a Lenta Corsa’s are launched, with one successfully reaching Quarto undetected and attaching a dummy charge to its hull, demonstrating the Siluro a Lenta Corsa’s effectiveness. Following this, Supermarina assigns three submarines, Iride, Gondar, and Scirè, to the 1° Flottiglia MAS.

In July 1940, Admiral Raffaele de Courten instructs Giorgini to select his four best crews for an assault on the capital ships of the Mediterranean Fleet in Alexandria. Although Giorgini protests that his teams are not yet adequately prepared, he proceeds with the mission. The operation, codenamed Operazione Golfo di Alessandria 1, ends in failure when, on August 22^nd, 1940, the submarine Iride is sunk by British torpedo bombers in the Gulf of Bomba as it prepares to depart. Giorgini, aboard Iride at the time, narrowly escapes alongside the Siluro a Lenta Corsa operators, but most of the submarine’s crew are killed. The Siluro a Lenta Corsa operators, including Tesei, Toschi, Luigi Durand de la Penne, and Birindelli, manage to rescue several survivors from within the wrecked submarine.

The Diver School in Livorno, operating within the Naval Academy, establishes itself in September 1940 under Tenente di Vascello Eugenio Wolk and Tenente di Vascello Belloni. Training includes the use of self-contained breathing apparatus and operational exercises against submerged targets.

In September 1940, a second attempt, Operazione Golfo di Alessandria 2, is swiftly planned with modifications. The submarine Gondar is equipped with pressurised containers to house the Siluro a Lenta Corsa’s, replacing the previous method of lashing them to the deck. Gondar departs from Messina rather than a lightly defended Libyan anchorage, as Iride had done. Leaving Messina on September 24^th, 1940, Gondar reaches Alexandria during the night of September 28^th, 1940 and September 29^th, 1940. However, Supermarina informs them that the mission is aborted because the Mediterranean Fleet has departed to escort a convoy to Malta. While en route to Tobruk, Gondar is detected and pursued by H.M.A.S. Stuart and H.M.S. Diamond. Severely damaged by depth charges, Gondar surfaces and is scuttled by its crew. Giorgini, along with the crew and Siluro a Lenta Corsa operators, is captured and interned in a prisoner-of-war camp in India, where he remains for nearly six years.

In November 1940, the first live test occurs when an MA/MAT explosive boat, carrying a reduced charge, launches against the decommissioned scout cruiser Quarto.

For a short while during the end of 1940 and at the beginning of 1941 the unit is renamed to Flottiglia MAS Speciale.

On March 15^th, 1941, it receives its final name the X^a Flottiglia MAS. The number in the name is chosen in honour of Julius Caesar’s favorite legion, the Tenth Legion. By that time Capitano di Fregata Vittorio Moccagatta is already commander of the unit and he reorganised it with an underwater and surface assault group. Besides these two assault units he also created several support units.

By March 1941, the unit’s organisational structure refines itself and slightly expands. The headquarters remains within La Spezia’s shipyard complex, while the surface operations division relocates to the Cottrau battery at the western end of the Gulf of La Spezia. The underwater division, meanwhile, splits between the Bocca di Serchio training base and the Divers School in Livorno, with personnel housed at the Naval Academy. Additionally, a detachment of the diver unit stations itself aboard the San Marco, an obsolete cruiser repurposed as a radio-controlled target ship, as well as the minelayer Fasana, both moored in La Spezia.

In April 1941, the Regio Marina launches an offensive reconnaissance mission in the waters off Corfu, specifically at Porto Edda. The operation, personally commanded by Commander Vittorio Moccagatta, involves two MAS torpedo boats, the MAS 539 and MAS 535, escorting two MTS motor torpedoes. The first MTS carries Lieutenant Commander Giorgio Giobbe and Sub-Lieutenant Aldo Massarini, while the second is manned by Sub-Lieutenant Renato Iovine and 2nd Chief Engineer Enrico Cerruti. However, unforeseen complications force the Italians to abort the mission before achieving its objectives.

On March 25^th, 1941, the Regia Marina successfully attacks Suda Bay, Crete, using six explosive-laden MTM boats under Lieutenant Luigi Faggioni. They infiltrate the bay at night and strike at dawn. One boat cripples H.M.S. York, forcing it aground, while another, piloted by Sergente Emilio Barberi, damages the oil tanker Pericles, earning him the Medaglia d’Oro al Valore Militare. A third boat hits a pier, while the rest suffer mechanical issues, leading their crews to scuttle them. Despite losses, the raid proves the effectiveness of small explosive boats in naval warfare.

A month later, on the night of May 25^th, 1941, and May 26^th, 1941,Operazione Baia di Gibilterra 3 is set to target the heavily defended naval base at Gibraltar. The operation relies on three Siluro a Lenta Corsa’s, deployed from the submarine Scirè. However, due to undisclosed reasons, the mission is cancelled before engagement. All operators return safely to base, and the attack on Gibraltar remains unrealised.

A major blow strikes X^a Flottiglia MAS in July 1941, during Operazione Malta 2, where the commander of the X^a Flottiglia MAS, Capitano di Fregata Moccagatta and Capitano di Corvetta Commander Giorgio Giobbe, head of the surface division, are killed in action. Capitano di Fregata Commander Junio Valerio Borghese, then in command of the submarine Sciré and the underwater operations division, temporarily assumes leadership. Shortly afterwards, Commander Ernesto Forza, a recipient of the Medaglia d’Oro al Valore Militare for actions in the Sicilian Narrows, takes command. Forza leads the unit until May 1^st, 1943, when Borghese, now promoted to commander, replaces him.

The unit’s structure continues to evolve, maintaining an emphasis on adaptability and efficiency. According to Admiral Forza’s notes, despite a broad range of assignments, the number of officers remains limited, ensuring operational flexibility. The latter half of 1941 sees the enhancement of the underwater division, with the establishment of the Gruppo Gamma, a diver unit, and the Special Ships Section, which works on modifying CA mini-submarines for underwater assault missions.

Until February 6^th, 1942, the Naval Staff retains direct control over X^a Flottiglia MAS. Thereafter, oversight transfers to the newly established General Inspectorate of the MAS (Generalmas), under Vice Admiral Aimone di Savoia, Duke of Aosta. This organisation, headquartered in Lerici, initially functions under the guise of overseeing motorboat and torpedo boat flotillas, but by April 1943, it officially assumes this role.

Advanced Bases

In the spring of 1942, Villa Carmela is established as a covert advanced base by X^a Flotilla MAS near Puenta Maiorga, Spain. Selected by Antonio Ramognino, a Regia Marina agent and former Piaggio technician, the location provides an ideal observation point for monitoring ship movements in Gibraltar Harbour. Situated a few dozen metres from the shore, it allows discreet access to the sea via a nearby dry stream bed, ensuring minimal risk of detection by Spanish authorities. Ramognino, having married a Spanish citizen, secures the house under the pretext that his convalescent wife requires rest in the warm climate of southern Spain. To aid reconnaissance, he installs a small parrot cage outside the house, facing the sea, which conceals an opening that allows him to monitor ship movements discreetly.

The base is conceived as an alternative to submarine-launched Siluro a Lenta Corsa operations, which are deem too costly and hazardous for attacking merchant vessels anchored outside Gibraltar’s boom defences. Previous missions have demonstrated that X^a Flotilla MAS operators can return to Spanish territory with relative ease, making Villa Carmela a strategic point from which Gruppo Gamma teams can carry out attacks with minimal exposure. To support these operations, it is planned to employ R boats, then under construction, designed to carry large explosive charges and reduce the divers’ strenuous swim to their targets.

Although the R boats are not yet available, Xa MAS launches its first Gamma operation from Villa Carmela, designated Operazione Gamma Gibilterra 1, on the night of July 13^th, 1942, and July 14^th, 1942. Twelve operators arrive from Italy aboard the Olterra and move to the base, from where they launch their attack the following night. The operation results in the heavy damaging of four steamers Meta, Shumma, Empire Snipe, and Baron Douglas). All Gruppo Gamma operatives successfully return, some reaching Villa Carmela, while others are apprehended elsewhere in the harbour. However, diplomatic intervention by the Italian authorities ensures their eventual repatriation.

Villa Carmela proves to be an effective launch point for these missions. The Gruppo Gamma operatives, fully equipped, reach the shore undetected via the dry stream bed and enter the water silently, avoiding the Spanish Carabineros patrolling the beach. Upon their return, the same route is used, and an old artesian well near the house serves as a discreet disposal site for empty tanks and other incriminating materials.

Around this time, Ramognino also proposes using the interned tanker Italian Olterra, moored in Algeciras, as an additional secret base for Siluro a Lenta Corsa operations against Gibraltar. Originally scuttled by its crew in June 1940 to prevent its capture, the Olterra is later salvaged and moored at Algeciras, where it appears to remain inactive. However, under the direction of X^a Flotilla MAS agent Antonio Ramognino, the ship is secretly converted into an advanced base for Siluro a Lenta Corsa’s.

To maintain the illusion of normalcy, the ship undergoes staged repair work, and a rumour is spread that it is being refurbished for sale. Meanwhile, the original crew is gradually replaced with X^a Flotilla MAS operatives and naval engineers, including Captain Engineer Travaglini. Hidden modifications include the installation of a secret underwater hatch cut into the port side hull, allowing divers to discreetly enter and exit the vessel. The forward hold is transformed into a clandestine workshop where Siluro a Lenta Corsa’s are assembled from parts smuggled in under the guise of boiler maintenance supplies.

Despite the presence of Spanish Carabineros stationed aboard to monitor neutrality regulations, the Olterra successfully avoids detection, enabling X^a Flotilla MAS to launch multiple underwater assaults against British shipping. Movements between Villa Carmela and the Olterra are carefully managed in small groups, using unfrequented roads and country lanes under the cover of darkness.

By mid-1942, recruitment expands beyond the Regia Marina to include elite personnel from other services. Efforts to improve operational range and carrying capacity lead to experiments with R class light motorboats and other tactical transport systems. The assault craft headquarters commissions CABI to develop a diver towing raft powered by an electric motor. While trials prove promising, the device does not reach operational status before the war ends. Similarly, Commander Wolk designs an inflatable raft, nicknamed the Turkey, which carries up to three operators and features a silent outboard motor. Although used in limited operations, it does not see widespread deployment.

Another late-war initiative involves the small CA-class assault submarines, intended to act as approachers for ‘Gamma’ divers. These submarines are designed to bypass harbour defences and facilitate the placement of large explosive charges. However, their operational effectiveness remains untested by the war’s conclusion.

Until mid-1942, the Livorno Diver School also trains Nuotatori (Divers) of the Regia Marina’s San Marco Regiment. Their instruction closely parallels that of the Gamma divers, though with an emphasis on coastal sabotage and raiding operations. Eventually, the Nuotatori (Divers) merge with Paracadutisti (Paratroopers) to form the Nuotatori Paracadutisti unit within the San Marco Regiment. While the NP remains under MAS Headquarters (Generalmas) until the armistice.

On July 14^th, 1943, the requisitioned fishing trawler Cefalo, manned by a militarised civilian crew, departs La Spezia on a covert mission known as Operazione Cefalo 1. Concealed beneath fishing nets and equipment, the vessel carries two MTSM light motor torpedo boats (222 and 230). The mission, commanded by Tenente di Vascello Corrado Dequal and Sottotenente de Vascello Corrado Garutti, is to patrol the waters south of the Balearic Islands, posing as a fishing vessel while awaiting an opportunity to attack Allied aircraft carriers that occasionally launch aircraft for operations over Malta.

For 16 days, the Cefalo remains on station, enduring rough seas at times. However, no enemy targets are sighted, and the mission concludes without any engagement. The vessel returns to base without deploying its assault craft, highlighting the challenges of intelligence-based naval operations dependent on unpredictable enemy movements.

From August 5^th, 1942 to August 8^th, 1942, the Cefalo conducts Operazione Cefalo 2, repeating its previous mission in the waters south of the Balearic Islands. As in July, the trawler, manned by a militarised civilian crew, carries two MTSM’s, concealed under fishing equipment, with the objective of ambushing Allied aircraft carriers operating in the area.

Despite maintaining its cover as a fishing vessel and patrolling the designated waters, no enemy targets are sighted. The mission ends without engagement, and the Cefalo returns to base without deploying its assault craft, mirroring the outcome of its first operation.

A second operation from Villa Carmela, Operazione Gamma Gibilterra 2, starts on the night of September 14^th, 1942. Three Gamma divers set out from Villa Carmela, successfully sinking the steamer Rovens Point. Two return safely to Villa Carmela and later rejoin the Olterra, while the third is intercepted by Spanish police. However, no information regarding the existence of the two advanced bases is compromised.

By 1942, surface training shifts to Muggiano, while additional facilities establish themselves in Brindisi, Leros, and Augusta. On September 3^rd, 1942, X^a Flottiglia MAS headquarters, along with subordinate departments and support services, also moves to Muggiano, on the eastern edge of the Gulf of La Spezia. The complex, previously a Regia Aeronautica seaplane base, provides an ideal location for operations, positioned near the San Bartolomeo torpedo works where underwater assault craft are assembled. The move enhances logistical efficiency, with improved access to essential resources. Meanwhile, existing training facilities in Livorno and Bocca di Serchio remain in use, and secondary bases establish themselves in Brindisi, Augusta, Leros, the Black Sea port of Foros, Taormina, Carloforte, and Amalfi as needed.

On the night of December 7^th, 1942, the X^a Flottiglia MAS launches Operazione Baia di Gibilterra 5, the first sabotage mission carried out from the Olterra. Three SLC teams covertly exit the ship through a hidden underwater hatch and infiltrate Gibraltar Harbour. They successfully attach explosive charges to multiple targets, including the troopship Raven’s Point and two other vessels, causing extensive damage. All operatives initially escape undetected; however, two are later arrested by Spanish authorities. Despite interrogation, they reveal nothing about the Olterra’s role as a covert base.

In April, 1943, the X^a Flottiglia MAS launches Operazione Huelva, a covert sabotage mission targeting British shipping in the Spanish port of Huelva. The operation is part of the GOG (Gruppi Operativi Gamma) strategy, aimed at infiltrating neutral ports and attacking enemy vessels. Italian operatives Salvatore Nizzi and Carlo Vianello, travelling under false identities, arrive in Huelva in February 1943 and board the Italian steamship Gaeta, which serves as their base. On April 6^th, 1943, they secretly receive explosives and diving equipment in preparation for their mission.

Their first attack attempt on April 22^nd, 1943 fails due to a malfunction in Vianello’s breathing apparatus, but they succeed the following night in planting explosives on a British vessel. Their most significant target is the Ladovich, a 9,700-ton freighter, which Nizzi reaches after swimming 3,000 metres. He attaches explosive charges before the ship departs on May 14^th, 1943.

As British security measures intensify, with hull inspections and diver patrols, further operations become more challenging. However, on June 13^th, 1943, Nizzi seizes an opportunity to sabotage a grounded British vessel, planting explosives before it refloats and resumes its journey.

Among the ships attacked, only the Ladovich is confirmed to have sunk, while the fate of the other vessels remains uncertain. After completing their mission, Nizzi and Vianello attempt to return to Italy via Madrid but are captured by British intelligence.

During the night of May 7^th, 1943, the X^a Flottiglia MAS launches Operazione Baia di Gibilterra 6, the second major sabotage mission from the Olterra. Using the same covert tactics as before, Siluro a Lenta Corsa teams secretly deploy from the hidden underwater hatch and infiltrate Gibraltar Harbour. The attack results in severe damage to the freighters Stanridge and Pat Harrison, once again proving the effectiveness of the Olterra as a concealed forward base.

In anticipation of an imminent Allied landing on either Sardinia or Sicily, the X^a Flottiglia MAS deploys various MTSM and MTM assault craft to strategic locations. Under the command of Capitano di Corvetta Aldo Lenzi, units are stationed in Sardinia at Cagliari, Carloforte, and Bosa Marina, with Tenente di Vascello Corrado Dequal and Tenente di Vascello Aldo Massarini serving as subordinates.
In Sicily, Augusta becomes the primary base of operations, where the surviving motorboats from Autocolonna Moccagatta from the Crimean campaign and Autocolonna Giobbe from the North African campaign are assembled under the command of Sottotenente di Vascello Ongarillo Ungarelli. However, when the Allied invasion of Sicily begins on July 10^th, 1943, Italian forces are immediately placed under immense pressure. The bases in Sardinia are swiftly decommissioned, and the assault craft stationed in Augusta, Sicily are forced into a rapid retreat northward.

The motorboats regroup in Mazzarò, near Taormina, where they are joined by Commander Lenzi, who is transferred from Sardinia to reinforce the remaining units. Light motor torpedo boats launch several attacks on enemy shipping operating along the eastern Sicilian coastline, though these engagements fail to produce any confirmed results.

As the Italian front continues to collapse under the advancing Anglo-American forces, the assault craft relocate first to Messina. Here, MTSM 262 becomes the final Italian naval unit to withdraw from Sicilian waters as the island falls completely into Allied hands. From Messina, the surviving vessels retreat further north, regrouping at Gioia Tauro before making their way to Amalfi.

Meanwhile, between 30 June and 2 August 1943, the X^a Flottiglia MAS conducts a series of covert sabotage missions under Operazione Stella, targeting Allied shipping in Turkish ports while maintaining secrecy to avoid compromising Turkey’s neutrality. Gruppo Gamma Diver Ferraro, under orders from Junio Valerio Borghese, arrives in İskenderun (Alexandretta) in May 1943 with false diplomatic credentials. To deflect suspicion, he poses as a non-swimmer for a month before launching his first attack.

On June 30^th, 1943, Ferraro, assisted by SIM agent Giovanni Roccardi, swims to the 7,000-ton steamer Orion in İskenderun and secures explosive charges to its keel. A week later, on July 7^th, 1943, the ship is destroyed along with its cargo.

On July 9^th, 1943, in Operazione Stella 2, Ferraro carries out another attack in Mersin, targeting the 10,000-ton steamer Kaituna. However, an inspection team discovers and neutralises an unexploded charge, preventing the ship’s destruction.

On July 30^th, 1943, in Operazione Stella 3, Ferraro places explosive charges on the British steamship Sicilian Prince in Mersin. This time, a thorough security sweep before departure leads to the discovery and disarmament of the devices.

On August 2^nd, 1943, in Operazione Stella 4, Ferraro returns to İskenderun and successfully sabotages the 5,274-ton Norwegian cargo ship Fernplant, sinking the vessel.

Shortly after, on August 3^rd, 1943, Operazione Baia di Gibilterra 7 is launched from the Olterra against British shipping in Gibraltar. This time, the target includes key British naval assets, notably the Fidelity and Harrison Gray Otis. Once again, the attack is a success, with Gruppo Gamma divers managing to attach explosive charges undetected. The resulting detonations inflict significant damage on the vessels, and all operatives successfully return to the Olterra without being discovered.

Post-Armistice

On the evening of September 8^th, 1943, Marshal Pietro Badoglio announces via national radio that Italy has signed an armistice with the Allies. The news takes the Italian armed forces, including the Regia Marina and its assault craft units, by complete surprise. The headquarters of the Comando Flottiglia, along with the largest concentration of personnel and vessels, is based in northern Italy, primarily in La Spezia, Bocca di Magra, and Livorno, close to the Ligurian and Lombard industries responsible for constructing and developing assault craft, such as ‘barchini’ and submarine self-propelled vessels.

The advange bases Olterra and Villa Carmela remain undiscovered until after the armistice. The Italian armistice halts plans to establish additional advanced bases in neutral harbours such as Barcelona, Malaga, Lisbon, and Porto, bringing further expansion efforts to an end.

Xa Flottiglia MAS of the Repubblica Sociale Italiana

In contrast, southern Italy and Sardinia house a mere twenty surface craft, deployed mainly for coastal defence. At the Muggiano headquarters of X^a Flottiglia MAS in La Spezia, Commander Junio Valerio Borghese faces the rapid disintegration of the navy’s shore infrastructure. This collapse follows the departure of the battle fleet from Ligurian bases and the scuttling of vessels that are unable to sail due to ongoing dockyard maintenance. Amid initial confrontations with German forces, Borghese manages to hold his unit together, ultimately forging an ‘alliance agreement’ between X^a Flottiglia MAS and German command.

Following the dramatic rescue of Benito Mussolini from captivity at Gran Sasso, the Repubblica Sociale Italiana is proclaimed. X^a Flottiglia MAS pledges its allegiance to the Repubblica Sociale Italiana, integrating into the Marina Nazionale Repubblicana, albeit maintaining a high degree of operational autonomy and a privileged relationship with the German Navy. By early 1944, Motoscafo Turismo Modificato’s are secured aboard the aircraft transport vessel Giuseppe Miraglia, likely as part of a transfer operation from Sardinia following the armistice.

In 1944, Italian and German forces conduct joint training exercises in Sesto Calende, on Lake Maggiore. A significant number of young volunteers flock to the X^a Flottiglia MAS base, drawn by its reputation and the desire to continue fighting the Anglo-American forces. To utilise these recruits, the core of submarine and surface assault craft expands to include naval infantry and raider (Nuotatori Paracadutisti, Parachutist Swimmer) units. These forces operate alongside German troops until the end of hostilities.

Under the command of Capitano di Corvetta Mario Arillo, X^a Flottiglia MAS continues commissioning various types of explosive and light torpedo motorboats. Some of these have been in service before September 8^th, 1943, while others are produced later in northern Italian shipyards, including SIAI, Baglietto, Caproni, and CABI-Cattaneo. Additionally, X^a Flottiglia MAS incorporates several Mas and motor torpedo boats that have been seized by the German Navy during the confusion of the armistice. These include modern Mas boats from the 500 class series (such as MAS 505, 525, 553, 556, 561) and two 60-ton motor torpedo boats. Although these vessels are not designed for assault operations, some, like MS 74 and MS 75, are modified as fast approachers for Motoscafo Turismo Modificato’s and Siluro a Lenta Corsa’s.

Throughout 1944, the surface assault units of the RSI’s X^a Flottiglia MAS, comprising fewer than seventy vessels, operate predominantly in the Tyrrhenian Sea. They are initially active in the Anzio-Nettuno area before shifting operations to the western Ligurian coast. In the Adriatic, their activities are limited to missions using craft transferred from the Germans, operating out of Istrian bases. Their original role of breaching enemy harbours has become impractical, so instead, they conduct surprise night attacks on small and medium-sized vessels in coastal waters. However, the technical limitations of these craft mean that while some successes are achieved, they are not strategically significant, and losses are substantial.

Resources remain critically scarce. Fuel, spare parts, and other necessities are in short supply, though the flotilla’s organisation manages to secure essential provisions most of the time. The diver units, consisting of ageing Siluro a Lenta Corsa’s and a few newly developed Siluro San Bartolomeo’s, are based in Venice and La Spezia, alongside a small contingent of divers from Gruppo Gamma. However, their operational effectiveness is severely hampered by the lack of suitable ‘approacher’ submarines and delays in the development of new CA-class vessels.

Mariassalto of the Regio Marina

The situation is markedly different in southern Italy. The Regia Marina manages to locate a small number of assault craft, thirteen Motoscafo Turismo Modificato’s and nine Motoscafo Turismo Siluri Modificato’s, in southern Italy and Sardinia. With these, a new assault unit, Mariassalto, is formed at Taranto San Vito under the command of Capitano di Vascello Ernesto Forza.

Maintaining operational readiness proves challenging, as all the suppliers of essential materials are in the German-occupied north. The shortage of spare parts, particularly for engines, is a major obstacle, which the dockyard at Taranto can only partially mitigate due to the lack of technical documentation and construction blueprints. Another issue is the lack of trained personnel, as most experienced operators have remained in the north. To address this, the Italian government, now a co-belligerent of the Allies, requests the release of captured assault craft operators. The request is swiftly approved, as the Anglo-American commanders are eager to integrate Italian expertise into their own special operations. With their superior industrial resources, the Allies see potential for large-scale applications of Italian assault techniques.

Mariassalto’s motor torpedo boats primarily conduct reconnaissance and clandestine missions, landing and retrieving agents behind enemy lines in both the Adriatic and Tyrrhenian seas. A planned attack using explosive motorboats on a German ship in Suda Bay, Crete, is cancelled due to persistent adverse weather conditions. However, Mariassalto does execute two joint operations with the Royal Navy against German-occupied Italian ports. The first, in La Spezia, involves Italian ‘approacher’ vessels, British Chariot-type underwater self-propelled craft, and Italian Gruppo Gamma divers. This mission successfully sinks the abandoned cruiser Bolzano. The second operation, in Genoa, involves Italian divers using loaned British Chariot Mk I craft in an attempt to prevent the Germans from scuttling the unfinished aircraft carrier Aquila to block the harbour entrance.

Aftermath

By the end of the war, most of the remaining operational assault craft of Xa Mas have been either destroyed or scuttled. While the Allies have already studied the capabilities of Italian surface craft, their primary interest shifts to underwater assault technology. The SSB, a successor to the now-obsolete SLC, attracts particular attention. In Venice, four SSBs in various states of completion are recovered. Comparative trials between an SLC and an SSB are conducted in the waters of the former San Andrea seaplane base, with assistance from former Xa Mas and Mariassalto operators.

Following these tests, two SSBs are shipped to Great Britain for further evaluation, while another two, along with an SLC, are transported to the United States. Accompanying them are some of the most experienced Italian operators, who participate in intensive trials at a US Navy facility. Recently declassified American documents, along with memoirs of Italian participants, suggest that the US briefly considers deploying Italian-inspired underwater assault tactics in the Pacific theatre against Japan. However, with the war in the Pacific concluding in August 1945, this possibility is never realised.