To the general public, and also to most historians, the activities of the 10th Light Flotilla were limited to the Mediterranean. In fact, in the first few months of the war, the unit focused solely on British targets within the Mediterranean. Unfortunately, the audacious but unwise attack against Malta on July 25th, 1941 wiped out not only a great number of skilled and trained officers and ratings, but also most of the command structure of the unit. The responsibility of continuing the activities of the 10th Light Flotilla fell on the commander of one of its two divisions, Commander Junio Valerio Borghese. This officer had already distinguished himself by skillfully delivering human torpedoes to both Gibraltar and Alexandria, and would become the heart and soul of the 10th Light Flotilla and later recount its history in a well-known book published after the war . Unfortunately, upon Italy’s surrender in September 1943, Commander Borghese opted to continue fighting along with the Germans in Northern Italy, evolving the 10th Light Flotilla into an anti-partisan land-based formation. At the end of the conflict, with imprisonment looming despite his Gold Medal for Valor received during the conflict , Borghese confined himself to Spain in a self-imposed exile, which lasted until his death.
A picture of New York on the Brooklyn side dating back to around 1928. The physiological damage caused by this attack would have been much greater than the actual physical one.
The role of Borghese in the 10th Light Flotilla would be an important one. This man was not just a commanding officer, but also a leader. As he would later write, he perfectly understood the value of “ the psychological effect on the Americans, who had not yet undergone any war offensive on their own soil ”. In his view, it was paramount to conduct an attack outside the Mediterranean. The idea was audacious, but realistic. The Germans had concocted similar plans relying on agent saboteurs to infiltrate the United States and damage critical production or manufacturing sites, but failed. These attacks were prevented by the highly developed American information system and by the insular nature of the American continent. The Japanese, well after the attack on Pearl Harbor, sent a submarine to bomb the California coast , causing minimal damage but much turmoil.
The Caproni CB, also produced by the Firm Caproni
The physiological damage caused by this attack would have been much greater than the actual physical one.
Borghese intended to bring war to the American continent by conducting an action that would be demonstrative in nature and which would have limited military value in damage inflicted, but enormous value in terms of psychological effects. The plan, to which today we have only limited documentation, called for the delivery of an insidious weapon off Fort Hamilton to then have this craft navigate upriver toward the Hudson River and deliver explosive charges to some of the merchant ships docked along West Street. Due to the nature of the harbor and the distance of New York from the nearest Axis-occupied port, the use of human torpedoes was not only unsuited, but also impractical. In the Mediterranean, the 10th Light Flotilla had used delivery submarine equipped with three cylindrical containers mounted on deck. Later, the cylinders would become four and would be installed to the side of the hull. The cylinders were used to protect the human torpedoes from the weather, but made navigation harder and, due to their size, increased the profile of the vessel, thus increasing the risk of being spotted. For the attack against New York, the 10th Light Flotilla would have had to employ a different craft, one designed for longer missions, one protecting its crew from the weather, but still one small in size and stealthy. The solution would be found in a warehouse in the military port of La Spezia.
The craft in question, known as a CA, was the invention of the firm Caproni, originally founded by Giovanni Caproni and well-known around the world for the construction of advanced airplanes, winners of many world records. During the crisis of 1935, when Italy was on the brink of war with Great Britain and during the same period when the Italian Navy instituted what would later become the 10th Light Flotilla, his firm was asked to collaborate with the Regia Marina in the construction of new assault weapons. This collaboration between the aeronautic firm and the Navy was unique, but it also allowed for the introduction of new and unique engineering ideas in the relatively rigid field of naval engineering. Caproni sought the collaboration of a trained naval engineer and he selected Vincenzo Goeta, an independent naval consultant with offices in Genoa. In a few months, the Goeta-Caproni project, as it will be later known, was presented to the Italian Ship Design Committee of the Navy, a reputable bureau led by General Umberto Pugliese, an extremely talented individual highly recognized for the invention of an underwater protection system which bears his name. The project presented to the Navy in early 1936, and eventually approved three months later , was encouraging, especially because the ideas proposed by the Caproni firm were exceptionally innovative. The project was given the name “G”, and called for a craft with a crew of two, powered by a diesel engine and capable of launching torpedoes.
Caproni called this craft a “submergible motorboat”, but in reality it was a submarine. In Caproni’s vision, this little craft was the equivalent of a fighter plane; his previous experience in the aeronautic field was an important factor in shaping both the craft and its possible tactical utilization. Unfortunately, the Navy was not quite ready to embrace these new and somewhat radical ideas, but at the same time they were still interested in pursuing “Project G”. As common during the period, the Goeta-Caproni team was assigned an engineer from the Ship Design Committee, Major Spinelli, to begin constructing two prototypes which eventually came to be known as CA 1 and CA 2 . Construction began in earnest at the Caproni factory located in Taliedo, near Milan. This miniscule submarine had a resistant hull with semispherical caps at each end. Ballast tanks, torpedo launchers, and other components were placed externally to the resistant hull. The project called for a crew of two; the commanding officer would sit on a special seat from which he had access to the periscope and the controls, mostly a joystick, just like an airplane, and also navigational instrumentation resembling more a cockpit rather than a control room. The enlisted man would instead crawl near the engine since there was enough room to stand up.
The first prototypes were delivered to the Navy in 1938 in total secrecy. Loaded on a special railcar, the odd-looking crafts were properly disguised and taken to Lake Iseo near Brescia and Bergamo. This is a relatively small lake with a depth of about 750 feet (251 meters) and a perimeter of about 60 kilometers. The lake is shaped like an S and has a relatively large island in the middle. Initial testing confirmed the good quality of the crafts and allowed for the correction of some defects, and the improvement of many components. Naturally, due to the absence of salt, buoyancy in a fresh body of water was different from the ocean, thus testing continued in Venice. At the arsenal of Venice, a military shipyard with a long and lustrous history, three young officers began the official testing. They were Lieutenants Torri, Gatti and Meneghini . Testing confirmed some already known issues, mostly related to the sensitivity of the controls , but the submarines were able to navigate on the surface at a speed of 7 knots, 5 knots while submerged, and repeatedly launched the two 450 mm torpedoes without many inconveniences.
Having completed the tests in Venice, the two submarines were sent to La Spezia, Italy’s largest naval base. Experience acquired during the testing of CA 1 and CA 2 induced the design team to increase displacement of about 4 tons, reaching the 20 ton mark. Meantime, the two prototypes were abandoned and placed in storage, the same storage where they would be found by the 10th Light Flotilla. Having been laid up for over two years, the two submarines were in poor condition. It was decided to send them back to the factory for a complete refurbishing, but also to make some changes. The refurbished CAs were redesigned to better fit the needs of the 10th Light Flotilla, thus the torpedo launchers were removed and replaced with eight 100 Kg explosive charges. These charges would be manually placed under enemy ships by a frogman. The diesel engine was also removed as the boats were expected to operate like a “human torpedo”, thus within the range of the electric motor. Further alterations included the removal of the conning tower and the periscope. With the combustion engine removed, the second crewmember became the operator of the explosive charges, also known as frogmen. The scuba equipment used was the same already employed by the operators of the human torpedo and consisted of a full-body rubber suit and a breathing apparatus fueled by pure compressed oxygen .
At the end of this work, the CA could have been considered a new craft. Range was limited to about 70 miles, underwater speed was increased to 6 knots and maximum depth was tested up to 47 meters: quite an achievement for such a small unit. Further testing brought forth more issues, some quite relevant. The explosive charges had been placed in the cavities left by the removal of the torpedo launcher at the base of the hull, but their position made the release of the charges themselves very difficult. Thus, the two cavities were eliminated and the charges were moved further up almost in line with the small deck. The hydraulic pump, made by the firm Calzoni, was found to be too noisy; this was a problem common to most Italian submarines. Thus, the pump was removed and replaced by one operated manually by one of the two crewmembers. During testing, CA 1 sank to the bottom of Lake Iseo due to a small failure and even if rescued, it would not be ready for action for quite some time. Thus, the 10th Light Flotilla was left with only one craft ready for action: CA 2.
Expecting the refurbishing of CA 1 to happen promptly, Commander Borghese envisioned two attacks to be carried out in the Atlantic; one against the British base of Freetown and one against New York. To deliver the midget submarines to their targets, Borghese needed submarines, but those already assigned to his unit were too small for oceanic navigation. Thus, according to his memoirs, Borghese attempted to obtain German submarines on loan from the Kriesgmarine, but it appears that Admiral Donitz, the commander of the German submarine forces, could not spare any. If a German submarine had been made available, the possibility of completing the attack would have been much greater because the U-Boats were newer, and more reliable and maneuverable than the rapidly aging Italian submarines.
During this period, the Italian Navy was still operating its Atlantic submarine base in Bordeaux and the Italian submarines were well suited for the task due to their large displacement, but were very limited in numbers. The commanding officer of the base was Rear-Admiral Romolo Polacchini, later replaced by Commander Enzo Grossi, famous for having claimed the sinking, later discovered false, of two American battleships. Polacchini, we are told, immediately made one of his boats available to Borghese, while later on, Grossi wholeheartedly provided support and encouragement to the operation. The submarine selected was the Leonardo Da Vinci, an oceanic vessel of the Marconi class commanded by Lieutenant Gianfranco Gazzana Priaroggia , one of the most talented Italian submarines, whose qualities were certainly appreciated by Commander Borghese, a submariner himself.
The Leonardo da Vinci with the CA seated in the special cradle.
The Leonardo Da Vinci was one of the most active submarines of the Italian fleet. On July 1st, 1942 it returned to base after a successful patrol in which it sank around 20,000 t. of enemy shipping. Upon its arrival in Bordeaux, the boat was sent to the local shipyard to be transformed into a transport submarine for the CA submarines. Under the direction of the chief construction engineer, Major Giulio Feno, the forward deck gun and its base were removed and a cradle created between the resistant hull and the deck superstructure. The midget submarine would rest in this cradle about one fourth below deck and the remaining portion sticking out, but without obstructing the view from the conning tower. Two large claws operated from inside the transport submarine secured the small craft. Although it is not known, it should be assumed that the mother ship was also able to provide the midget submarine with power to recharge or tip off the batteries.
Trials began in September 1942. On the 9th, the Leonardo Da Vinci with its load on deck went out to sea to experiment with the release and recovery of the midget submarine. The same difficult and tedious maneuvers were repeated until the 15th of the same month when the whole process was proven not only doable, but also successful. The Leonardo Da Vinci could have left for New York in a few days, but it was too early. The plan called for action in December, when the daylight is minimal and the darkness of the night gives the operators more time to penetrate the enemy port and place the explosive charges. Also, the Italians had minimal knowledge of the situation in New York and were looking for more intelligence. For reasons unknown to us, the mission against New York was postponed until December 1943 ; it would never take place. Some secondary sources claim that Borghese had decided to wait for the completion of CA 3 and CA 4, two newer and more advanced midget submarines. Meantime, on May 6th, T.V. Gazzana Priaroggia was promoted “for service in war” to the rank of Lieutenant Commander and a few days later, on May 22nd, the Da Vinci launched the last radio signal informing the base that the following day it would begin “hidden” navigation. The boat was expected to arrive in Bordeaux within a week, but it would never arrive. In 1945, the English Admiralty confirmed that on May 23rd 1943 at 11.35 (T.M.G.) the destroyer “Active” and the frigate “Ness ” conducted an attack just off Cape Finestrelle. There were no survivors and the 10th Light Flotilla had lost its transport submarine and the only captain trained to release and retrieve the CA.
The CA2 the way it was found in Bordeaux after the war.
A few months later, on September 8th, Italy would sign the armistice with the Allies. Most of the Navy followed the clauses of the armistice, and even if officially open, the base in Bordeaux ceased to exist. The CA remained in Bordeaux under German control and, when the city was evacuated in 1944, it was left behind. In 1945, CA 2 was found in Bordeaux on a flatbed railcar resting on wooden blocks and secured by two chains. The hull of the craft was almost intact, including the propeller, but all the control surfaces had been removed. It is not known when, but the small submarine was scraped. The remaining vessels of the CA class were also lost, some in circumstances still unknown, thus all we have left of their history is a few fading pictures. After the armistice, both the Royal Navy and the U.S. Navy became very interested in the 10th Light Flotilla and studied their tactics scrupulously. The legacy of this small group of men lives on in the special forces of most navies.