An Italian CB-class submarine
Although the presence of midget submarines on both sides was rumoured during the Russo-Japanese War, the Italian Navy may claim to have been the first to deploy midgets in 20th-century warfare. During World War I, a few small submersibles of c.16 tons (16.25 tonnes) surfaced displacement were constructed and, having proved unsuitable for operations outside sheltered waters, were used for harbour defence in the Adriatic. These pioneer designs were dusted off in the mid-1930s when, at the time of Mussolini’s venture into Abyssinia (now Ethiopia), conflict with Great Britain temporarily threatened. A weapon for clandestine penetration of such British Mediterranean bases as Malta, Gibraltar and Alexandria was advocated by many Italian officers, with Cdr Angelo Belloni, a leading spirit in the training of volunteers for the Decima Flottiglia MAS (10th Light Flotilla), the Italian Navy’s “special attack weapons” unit, prominent among them.
In the event, the Maiale (“Pig”) manned-torpedo was to be the major penetration weapon; but in the pre-war years it was planned that midget submarines should penetrate enemy bases, either to carry out torpedo attacks or to release frogmen to place explosive charges. In conditions of strict secrecy, the Italian Navy constructed and had operational by April 1938 the midget submarines C.A.1 and C.A.2 (C=Costiero-tipo, “coastal-type”), built by Caproni, Taliedo of Milan.
In their original form, C.A.1 and C.A.2 were two-man boats displacing 13.5 tons (13.7 tonnes) surfaced; 32.8ft (10m) long overall; 6.43ft (1.96m) in beam; and drawing 5.25ft (1.6m). On the surface, a single-shaft 60hp MAN diesel gave a maximum speed of 6.5kt (7.5mph, 12kmh) and a range of 700nm (805 miles, 1295km) at 4kt (4.6mph, 7.4kmh). Submerged, a 25hp Marelli electric motor gave a maximum 5kt (5.75mph, 9.25kmh) and a range of 57nm (65.5 miles, 105km) at 3kt (3.45mph, 5.5kmh). Armament consisted of two 17.7in (450mm) torpedoes in external dropping gear.
Trials soon showed that C.A.1 and C.A.2 were not capable of operations involving sea passages of any distance. Nor was there much chance of the midgets surviving independent missions in the clear, shallow, inshore waters of the aircraft-dominated Mediterranean. In 1941, it was decided that the midgets must be carried to their target areas on mother boats and released under cover of darkness to penetrate defended anchorages and lay explosive charges. The diesel units were removed from both midgets, as were the torpedo racks. This reduced displacement to 12 tons (12.2 tonnes) surfaced and 14 tons (14.2 tonnes) submerged; increased maximum submerged speed to 6kt (6.9mph, 11kmh) and submerged range to 70nm (80.5 miles, 129km) at 2kt (2.3mph, 3.7kmh); and permitted a crew of three to be carried; at least one a trained “frogman”.
The Leonardo da Vinci with the CA seated in the special cradle.
Date: December 1943
Place: Hudson River, New York, USA
Attack by: Italian midget submarine “C.A.2”
Target: Shipping at anchor and dock installations
Urged on by the German high command, who stressed the moral effect on the Allies of increased Italian naval effort in the Atlantic, Cdr Prince Junio Valerio Borghese, commanding the 10th Light Flotilla, planned spectacular and potentially suicidal missions for the Italian midgets: attacks on the British base at Freetown, Sierra Leone, on the west coast of Africa – and on harbours along the east coast of the United States. The Freetown plan, for which C.A.1 was allocated, was abandoned when it was decided that British defensive measures allowed no chance of success; but the operation against the USA, with New York specified as the target for maximum psychological effect, reached an advanced planning stage.
In mid-1942, in preparation for the New York raid, C.A.2 was transported overland to Bordeaux, where “Betasom”, headquarters for Italian submarines operating in the Atlantic, was commanded by Capt Enzo Grossi. There, too, came the Marconi-class submarine Leonardo da Vinci of 1,190/1,489 tons (1209/1513 tonnes), selected as the midget’s carrier. Under the direction of Cdr Borghese and SubLt Massano, Italian workshops at Bordeaux under Major (naval rank) Fenu removed Da Vinci’s 3.9in (100mm) gun and in its place, just forward of the conning-tower, constructed a semi-recessed “pouch” with retaining shackles for C.A.2. This arrangement led to the mother boat being designated the Canguro (“Kangaroo”). Sea trials under Borghese’s command proved to his satisfaction that the midget could be launched from the submerged Kangaroo and could be recovered when the mother boat surfaced beneath it. The latter point was important in avoiding any indication that the projected mission was regarded as suicidal: just so had the IJN made “official” plans to recover its midgets after Pearl Harbor.
According to Borghese, the Kangaroo (not Da Vinci, which was sunk by British warships off the Azores in May 1943) would launch its midget while submerged off New York Bay. C.A.2 (or, in the later stages of the operational planning, the near-identical C.A.3 or C.A.4) would make its way by night into the crowded harbour at the mouth of the Hudson. Two of the three crewmen, in frogmen’s gear, would leave the boat to plant time-fuzed explosive charges – eight 220lb (100kg) charges and twenty 4.4lb (2kg) “limpets” were carried – under ships and against dock installations. Then C.A.2 would slip downriver to make rendezvous at sea with the Kangaroo.
The suicidal nature of the plan is obvious. Borghese made the airy assumption that New York’s harbour defences “against such a surprise attack presumably didn’t exist” – although the “happy time” enjoyed by German U-boats off the American east coast in the earlier part of 1942 had resulted in much-improved anti- submarine patrolling. The Kangaroo would have to surface in American coastal waters to allow the midget’s crew to enter their craft, since they had no means of access from the mother boat; and it would have to surface again offshore, in the aftermath of the attack, to retrieve the midget. Finally, it was estimated that the midget itself, with a submerged capability – for C.A.2, C.A.3 or C.A.4 – of no more than 70nm (80.5 miles, 129km), might need to remain in the Hudson for up to two days. Yet, according to Borghese, only Italy’s collapse in September 1943 prevented the mission from being carried out, as planned, in December of that year. As well as the four C.A.-type boats, the Italian Navy built 22 midgets of C.B.-type (some of them completed under the Italian Fascist Republic in 1943–44). These four-man boats of 36/45 tons (36.6/45.7 tonnes) were not used for “special attack” missions but for conventional torpedo operations. In this role, they had some success in the Black Sea, where a six-strong flotilla operating from the Romanian port of Constanta is credited in Italian and German records (at variance with other sources) with sinking the Soviet submarines Shch. 208, in June 1942, and Shch. 207 in August 1943.