Pola - 1918,
affondamento della corazzata "Viribus Unitis"
Alessandria - 1941,
affondamento della corazzata "Queen Elizabeth" (Siluro Lenta Corsa
detto "Maiale")
Genesis of the design
In October 1935 two engineer officers, Sub-Lieutenants Teseo
Tesei and Elios Toschi submitted plans for an improved version of the Mignatta
to Admiral Cavagnari, Chief of the Supamarina, the Italian Naval Staff.
Cavagnari approved the idea and work began at La Spezia. Three months later the
prototypes were ready. Toschi described the craft as:
... in reality a miniature submarine with entirely novel
features, electrical propulsion similar to an aeroplane ... The crew (pilot and
assistant) instead of remained closed and more or less helpless in the
interior, keep outside the structure. The two men, true fliers of the
sea-depths astride their little underwater aeroplane, are protected by a curved
screen of plastic glass ... At night, under cover of darkness and steering by
luminous instruments, they will be able to attack the objective while remaining
invisible to the enemy . . . They will be able to cut nets and remove any
obstacle with compressed air tools and reach any target. . . with long range
breathing sets they can operate at depths down to 30 meters and can carry a
powerful explosive charge into an enemy harbour. Invisible and undetectable by
the most sensitive acoustic detectors, the operator will be able to penetrate
inside the harbour and find the keel of a large ship, attach the charge to it
and ensure an explosion will sink the vessel.
There was, however, no requirement for such a craft in
Italy's Abyssinian adventure so the weapons were stored and their crews
assigned to other duties. But by the summer of 1939 it was clear that a European
war was imminent, so the 1st Light Flotilla was formed in June under the
command of Capitan di Fregatta Paolo Aloisi with instructions to:
... train a nucleus of personnel for employment with given
special weapons and of carrying our ... experiments and tests concerned with
perfecting the said weapons.'
Aloisi was succeeded in command by Capitan di Fregatta Mario
Giorgini on the outbreak of war who in turn was succeeded by Capitan di
Fregatta Vittorio Moccagatta in March 1941. Under Moccagatta's leadership the
organization ceased to be part of the 1st Light Flotilla and became the 10th
Light Flotilla, Decima Mas, in its own right. This is the name by the which the
unit will be referred to in these pages. Moccagatta further split Decima Mas
into two parts: a surface and a sub-surface weapons group. The former dealt
with the operation of the fast explosive motor boats, and the latter with human
torpedoes and Gamma assault frogmen.
A base was established on a secluded stretch of land on the
Boca di Serchio and the officers and men involved in the initial tests were
recalled from their units. Cavagnari had taken the decision to order twelve
prototypes and at the beginning of 1940 the first successful exercises were
held, with the old cruiser Quarto as the target, in the Gulf of La Spezia.
These were successful and although two of the craft broke down, the third
attached a dummy charge to Quarto which would certainly have resulted in her
destruction. The concept had become a reality. However, the loss of two years'
research and development time meant that when Italy declared war on 10 June
1940, the weapon was still in an experimental stage and few were available for
operations.
Construction and
machinery
What was the craft which Decima Mas was to operate so
successfully? It was officially known as Siluro a Lenta Corsa (SLC) but the
name by which they will be forever be known is Maiale (`Pig'). During early
trials Tesei had to abandon a sinking SLC and came to the surface with the
words, `That swine got away!'. The name stuck. The craft was 7.3m long overall
which included the 300kg warhead at the front which was 1.8m long. The diameter
of the craft was 0.53m. The two operators sat astride the craft, the driver in
front with the No.2 behind. Beneath the driver's seat was the forward trimming
tank. Between and beneath the two seats was the battery consisting of thirty
60v cells. At a speed of 4.5kts the Maiale had a range of 4 miles and at 2.3kts
15 miles.
Inside the after portion of the craft was the l.lhp (later
increased to 1.6hp) electric motor and the stern trimming tank. At the stern
was the propeller, with hydroplanes and a vertical rudder, both surrounded by a
protective shroud.
The two operators sat behind shields to lessen the water
resistance. The driver controlled the craft by means of a joystick which worked
both rudder and hydroplanes. Speed was regulated by a fly-wheel connected to a
rheostat. Between the two operators was the quick-diving tank which was flooded
by lever action from the No.2's position and blown by compressed air from a
compressed air cylinder. Behind the No.2's seat was a locker containing net
cutters, a set of working tools, plenty of rope and clamps used to attach the
warhead to the hull of the target. The operators wore a one-piece `Belloni'
suit and breathed oxygen through a closed-cycle breathing apparatus
(Autorespiratore ad Ossigeno) which left no tell-tale trail of bubbles on the
surface. The apparatus consisted of two high-pressure oxygen cylinders which
gave about 6 hours' breathing time. The oxygen was fed, via a reducing valve
and a flexible tube, into the operator's mouthpiece. The operator exhaled
through the same tube and the `exhaust' air was cleaned in a cylinder
containing soda lime crystals.
The 300kg warhead (some later Maiale could carry two 150kg
charges) at the front of the craft was held in position by a metal clutch. The
procedure for attaching the warhead to the target was for the driver to
position the Maiale directly under one of the target's bilge keels. The No1
would then dismount and secure a clamp to the keel to which was attached a
length of rope. The driver would then move the Maiale forward under the hull
while the diver swam round and attached another clamp to the bilge keel on the
other side of the hull. He would then return and attach both cables firmly to
the warhead and set the fuse -a setting of 21/2 hours delay was possible. When
all was secure, he would give the appropriate signal and the driver would
release the warhead, so that it hung under the target's hull, suspended from
the bilge keels. The operators would then get clear.
Modus operandi
Initially the Italians thought of delivering the Maiale to
the operational area by air using a Cant Z.511 flying-boat. This idea was
swiftly abandoned, although it is interesting to note that in turn the British
and Germans both considered the possibility of delivering underwater assault
craft by air. Instead Aloisi turned to the submarine as the most likely means
of delivery. The old boat Ametista was fitted with pressure-tight containers on
her casing in which the Maiale would be kept on passage. When the submarine was
near the target area, the Maiale would be removed from the containers and
released to proceed on their own. Following the success of trials with
Ametista, three such containers were fitted to the submarines Iride, Gondar,
Scire and Ambra. Initially the submarine would surface to launch the SLCs, but
the Italians quickly developed quite sophisticated exit/re-entry techniques so
that the operators would leave the parent boat through the fore hatch while it
was sub-merged. This, of course, reduced the risk of the boat being caught on
the surface with the containers open and the Maiale and their crews on the
casing. An important feature of the Maiale containers was that they were built
to the same constructional standards as the submarine's hull so that the
commanding officer would not have his freedom of action constrained a specially
converted motor boat, Motosiluranti. Two such MTBs were converted and could
carry a Maiale on a specially-configured stern ramp, from which it would be
slid into the water stern first.
A feature of Maiale operations was the development of covert
bases near to the British base at Gibraltar. The Italians reasoned that to
maximize the use of the Maiale it was uneconomic and risky to deploy them from
a large transport submarine for every operation. Targets reported by Italian
coast watchers in Spain might have moved on by the time the submarine reached
the area, and furthermore the operators got `stale' in the passage to the
target area. What was wanted was a base on the British doorstep from which they
could launch repeated attacks with impunity.
They were fortunate in that the Spanish authorities turned a
blind eye to their activities. For Operation BG.3 in May 1941 the Maiale
operators went overland to the Italian tanker Fulgor from which they
transferred to the submarine. The same modus operandi was used in Operation
BG.4 in September 1941. But the Decima Mas planners, and a young Maiale
operator TV Licio Visintini, wanted to take this idea one stage further and
develop a fully-operational Maiale base overlooking Gibraltar harbour. For this
purpose neither the Fulgor nor the Villa Carmela - a house in Algeciras also used
by Italian Gamma swimmers to attack shipping at Gibraltar were suitable. The
Fulgor lay too far away at Cadiz and, in any case, any attempt to move her
nearer to Gibraltar would arouse the suspicion of the British. The Villa
Carmela was but could not he used regularly for operations and it would be out
of the question to take the Maiale directly to the beach for launching from
there. Such a course of action would stretch the patience of the Spanish
authorities too far.
Instead Visintini focused on the Italian tanker Olterra
lying at Algeciras. She had been scuttled by her Italian crew on the outbreak
of war but had been refloated by the Spanish and secured inside the breakwater.
A guard consisting of a corporal and four privates of the Guardia Civilia was
mounted to prevent all unauthorized personnel boarding the ;hip. In March 1941
members of the Olterra's original crew including Paolo Denegri, the Chief
Engineer, returned the ship to act as a care and maintenance party. The
Italians were provided with special passes allowing them to board the ship.
Visintini arrived onboard Olterra on 27 June 1942 with civilian papers
identifying him as Lino Valeri, the prospective First Officer of the Olterra.
He brought three technicians with him and also a medical technician. These four
men were to become the core of the Olterra’s Decima Mas detachment and would
remain on the ship until operations ceased in September 1943. Visintini lust no
time in getting to work. Four members of the Olterra’s mercantile crew- were transferred
to another ship on the ground, that they were indiscreet. At the same time
Visintini banned the Spanish guards from Visiting the forward part of the ship
on the grounds that he suspected them of stealing- food. Denegri and the three
`technicians' fulfilled a number of roles.
Preparing the Maiale was their most important function
together with acting as `dressers' for the operators, but they also under took
a number of other tasks including daytime reconnaissance of shipping in
Gibraltar (they were often spotted by British agents doing this) by telescope
from the ship's bridge and acting as enforcers to keep away any curious
Spaniards.
With the unreliable elements of the crew dismissed and the
Spanish guard confined to the stern, Visintini briefed those remaining on
Olterra’s new role as a base for Maiale operations against Gibraltar. In order
to facilitate operations of the Maiale a forward bulkhead was cut and hinged to
give access to the forepeak. Torpedo racks were manufactured ashore in Algeciras
and assembled in the forepeak. Finally the tanker was trimmed down by the stern
to allow the cutting of a hinged trapdoor measuring 5ft x 8ft in the hull. The
cutting took about two hours after which the trim was returned to normal so
that the opening was hidden below the waterline. The cutting party was hidden
by pontoons and stages moored alongside for painting and minor repairs to the
ship's hull. Cables for charging batteries were brought from the dynamos at the
stern concealed inside water pipes. The Maiale were broken down into their
component parts and packed into wooden crates, together with mines, Belloni
suits, clamps, oxygen cylinders and all the other equipment needed for Maiale
operations, and shipped to Algeciras by road directly from Italy. Some of the
crates were labeled as engineering spares and at least one box was filled with
boiler tubes and left with one end opened for the benefit of the curious. Other
material was collected by Denegri from the Italian Embassy in Madrid where it had
been sent by diplomatic courier. On another occasion a member of Olterra's crew
was granted compassionate leave to return to Italy. On his return he brought a
crate of limpet mines with him. The arrival of such a large amount of equipment
officially destined for a derelict tanker did not apparently arouse the
slightest suspicion or concern among the Spanish authorities. The use of the
Olterra as a covert base for Maiale operations was and remains one of the most
audacious stories of the Second World War.
Maiale operations
The Regia Marina employed Maiale against British targets at
Alexandria and Gibraltar. Space precludes a description of such operations and
excellent accounts exist in both English and Italian. The table below gives a
list of their successes but does scant justice to the effect these operations
had on the British. The Maiale and their operators were rightly respected. In
1943 a young Italian naval officer, Gino Birindelli, who been captured during
the Maiale attack on Gibraltar in October 1940, was due to be repatriated to
Italy on health grounds. Just as he was about to set foot on the repatriation
ship, he was seized by Military Police and put on the next POW transport to
Canada. The Admiralty considered that even in his weakened condition he could
not be allowed to return to Italy to give others the benefit of his experience.
This is an impressive total under any circumstances but
reflecting on these operations, Admiral Gino Birindelli, who had been captured
in Operation BG.2, considered that the Italians failed to make the most of this
weapon. Decima Mas Maiale attacks were planned to inflict the maximum damage
possible but little or no consideration was to given to the wider Axis plan of
campaign. Birindelli offers the opinion that the successful GA.3 operation, if
combined with a successful land offensive, could have had effects out of all
proportion to the scale of the operation. Sadly Italy's lack of economic muscle
and shortage of strategic materials did not permit this sort of grandiose
planning. Decima Mas had the capacity to be a strategic weapon but ultimately
it could never be more than a highly effective irritant. Nevertheless the
Italian flair for this sort of underwater warfare had been amply demonstrated.