Design

Design and Development 1919-1943

The first Italian submarines built after the Great War were the four of the Balilla-class from a design by engineer Cesare Laurenti (1865-1921). They were laid down in 1925 and completed in 1928-1929. Up to that time, these were the largest submarines built for the Regia Marina. They had a surface displacement of 1,450 tons and were armed with six torpedo tubes (four forward and two aft), a deck gun of 120/27 calibre (later changed to 120/45), and four machine guns. One of them (Sciesa) could even launch mines from a stern tube. Initially ordered from the Ansaldo Works, they were built by the Odero-Terni Works at La Spezia, and by the outbreak of the Second World War, they had become obsolete, although they saw limited service. Four medium-sized submarines of the Mameli–class were laid down in 1925 and completed in 1929. Designed by engineer Virginio Cavallini (1875-1944), they had a partial double hull with saddle tanks, a surface displacement of 830 tons, an armament of six torpedo tubes (four forward and two aft), a 102mm/35 deck gun, and two 13.2mm machine guns. They proved to be a robust design, and Mameli set a world record when she dived at a depth of 117 metres during trials on 29 March 1929. The three surviving units of the Mameli-class were still operational in 1945 and crossed the Atlantic to be used for training exercises with the US Navy. This robustness would be typical of all Italian submarines, and during the Second World War, commanders would not be averse to taking their boats below a depth of 100 meters to escape depth charges. The commanding officer of Berillo believed his submarine may have reached a depth of 220 metres during the action that resulted in her loss (2 October 1940). This could not be verified as the depth gauge did not register beyond 135 metres.

The Mameli class was followed by four more of the Pisani class, slightly larger than their predecessors and designed by engineer Curio Bernardis. Bernardis was not a newcomer to submarines, having designed the Nautilus class (1911-1913) and the minelayers X.2 and X.3 inspired by the Austrian submarine U-24. The Pisani class was a single hull with internal fuel tanks. The design did not prove successful due to stability problems. Cavallini, Bernardis, and Laurenti competed for the building of Italian submarines and the succeeding classes. Cavallini improved the Mameli with his Settembrini class, Bernardis designed the Bandiera class derived from the Pisani class. An ocean-going submarine, the Calvi class, followed the Laurenti design.

More designs followed (see Classes section). Among the most serious flaws in the design of Italian submarines were the massive conning towers of their large submarines, which made them visible at a distance and enabled more than one of their prey to escape their clutches. Another problem was the lack of separate air intakes for diesel engines, which forced the submarines to proceed on the surface with their hatches open. In heavy seas, this could lead to sudden flooding and may have caused the accidental loss of more than one submarine. The problem was partially remedied in 1941 when air intake tubes were installed and conning towers were modified, although they still remained massive by German standards. Diesels were often observed to smoke excessively, disclosing the presence of the submarine from a distance.

The air conditioning systems were inadequate. The problem was not corrected by the outbreak of the war, causing the first fatality in the service and the first loss of a submarine through emanations of methyl chloride fumes. The slow diving speed (90-120 seconds), being the norm, made Italian submarines particularly vulnerable to air attacks. This often forced them to resort to fighting it out on the surface—usually a losing proposition.

Torpedo armament

The main submarine weapon was the torpedo. This was not always the case; Lothar von Arnauld de la Perrière, the Great War and all-time submarine ace, sank more ships by gunfire than by torpedo. During the Second World War, the gun became obsolete. The surfaced submarine was becoming increasingly vulnerable to air attack and radar, making the use of the gun difficult, at least for Axis submarine fleets. Most Italian submarines were fitted with four bow tubes and two to four stern tubes of 533mm, but there was a serious shortage of torpedoes for the surface and submarine fleets alike. From the start of the war, production was reputed to be only fifty torpedoes per month. This problem particularly affected torpedoes carried by submarines, as the reserve was only fifty percent of the total torpedo tubes mounted.

In June 1940, 1076 torpedo tubes of the 533mm caliber were mounted on Italian warships. Of these, 680 were mounted on submarines, and the remainder were distributed on cruisers or destroyers. A total of 1689 torpedoes were available. Since most submarines carried reloads, this meant that the actual number of torpedoes required by the undersea fleet at full strength was a little over 1,000. As surface ships required an additional 400, the theoretical reserve was less than 300.¹

On the other hand, the supply of 450mm torpedoes was adequate. There were 1971 available for a total of 362 torpedo tubes distributed on the X.2 and H–class submarines; the torpedo boats, motor torpedo boats (MAS). Even the Luftwaffe later used them in their torpedo bombers.

It must also be noted that the 450mm torpedo was significantly cheaper to produce than its 533mm counterpart (a cost of 60,000 lire against 300,000 lire²).

To circumvent the shortage of 533mm torpedoes, a bow, and a stern tube were adapted with ring-liners on each submarine to use 450mm torpedoes³. Since these torpedoes did not have the same speed as the 533mm ones and had a much shorter range, it added unnecessary complications to solve the problem of computing the correct attack angle when mixing the two types in a salvo. The 450mm torpedo had a significantly smaller explosive charge than their 533mm counterparts. This may explain why certain merchant ships required several torpedo hits before they sank. Initially, only contact pistols were used, so the torpedoes lacked the destructive power provided by magnetic ones, but at least were reliable. In the Mediterranean, the submarines were usually instructed to keep two bow tubes and one stern tube flooded during the night in readiness for a snap attack should the occasion materialise. Yet, night training was infrequent, although tactical conditions during the war made night attacks more favourable.

The Italians were not novices at designing torpedoes. Their Whitehead manufacture at Fiume was the oldest in the world, with the first self-propelled model built in the 1860s on a design by the British engineer Robert Whitehead and Giovanni Luppis of the Austrian Navy. Initially, the Italian 533mm torpedoes achieved the remarkable speed of 50 knots, but at the cost of accuracy. Tests revealed that thirteen percent of the torpedoes fired had an irregular course. Reducing the speed to 48 knots limited the incidence to five percent, which was considered satisfactory. During the war, a number of torpedo attacks were reported to have experienced an irregular course. As Italian submarine commanders favoured attacks using gyro-angled torpedoes, it was difficult to assess if the problem was due to a defective torpedo or a failure by the commanding officer to correctly calculate the attack data. In any case, this problem was relatively minor and cannot be compared to the troubles experienced by German and American submariners with their torpedoes during the early part of the war.

By the end of the summer of 1940, it was evident that the prospects of a quick victory against England had evaporated. The shortage of torpedoes had become so acute that, on 20 July 1940, Admiral Falangola, head of Maricosom (Submarine command), ordered all Mediterranean submarines not to carry reloads. Through the capture of documents, this was known to British Intelligence. It was suspected that Italy had supplied Germany with torpedoes during the Phoney War, this proved to be unfounded. The order appears to have remained in force until the Armistice in 1943, even though, Italian submarines were being equipped with German G7e (electric) torpedoes. These torpedoes had the advantage of being trackless so that the target had little time to take evasive action. It also eliminated the fear that escorts would comb the tracks to deliver a deadly counter-attack. The main drawback was their relatively slow speed (about 28.5 knots versus 48 knots for Italian torpedoes), requiring constant maintenance. The electric torpedoes made their appearance during the PEDESTAL convoy battle (better known in Italy as the Battle of Mid-August 1942), but it was only in November 1942 that their use became widespread. The common practice was to have the bow tubes armed with G7e torpedoes, while the stern tubes were armed with 533mm torpedoes of Italian manufacture. The 450mm torpedoes were phased out from front-line submarines, except for midget submarines and submarines of the Cagni class, which were armed solely with 450mm tubes. In the second half of 1942, magnetic pistols (of S.I.C. type) were introduced for Italian torpedoes, which increased the weapon’s effectiveness as an explosion a few metres away from the hull caused significantly more damage than a contact hit.

The French Navy was considered the main rival to the Regia Marina. Both submarine fleets had many similarities, but the French favored torpedo platforms that could be rotated at different angles, while the Italians preferred angling their torpedoes (as did American submarines).

British submarines had the possibility of angling the torpedoes 90°, but the practice appears to have seldom been used. The preferred method was to point the submarine toward the target and fire torpedoes at intervals of a few seconds. As a submarine could only turn at about one degree every two seconds, it could take six minutes to make a 180° turn. This handicapped several classes of their submarines, which had only bow tubes but, in practice, did not have much effect since stern attacks were rare. Overall, the British design perhaps made more sense than that of Italian submarines, which usually had four tubes forward and two to four tubes aft.

The Italians had neither a rigorous teaching system like the ‘Perisher’, favoured by the Royal Navy, nor a computer to calculate the firing angle. They had to rely on complex tables for firing their torpedoes. Hit-and-run tactics were the rule in the Mediterranean. This may explain the poor performance of their submarines under stressful situations in this theatre. In the Atlantic, particularly in the western seaboard and the southern areas where convoys were rare, submarines had more time to develop their attacks. They could linger in the area after a torpedo hit to finish off their victim, a luxury that their Mediterranean counterparts could ill-afford.

Was the torpedo shortage a factor in the lack of success of Italian submarines in the Mediterranean? At first glance, this does not appear to be so. The number of submarines returning from patrol with empty tubes during the war was insignificant: Ascianghi (once), Diaspro (twice), Platino (twice), and Tembien (once). However, there is no doubt that the shortage of torpedoes forced Italian submariners to be parsimonious in their use. One may also question the decision to often send them on short missions where most of their time at sea was spent travelling to and from their assigned patrol area.

The torpedo shortage did not affect the Betasom submarines to the same extent. The reason may have been that, contrary to the Mediterranean theatre, there was no lack of targets in the Atlantic. Patrols were also much longer, and on a few occasions, torpedoes were supplied at sea. In some rare instances, following the German method, three extra spare torpedoes were carried out in containers on deck. They did not always carry a full complement of spares, as a shortage appears to have been experienced briefly in 1942 when, in a few instances, only a partial set of reloads was carried. Reloading time was said to be approximately two hours. For 533mm models, depth-setting could be adjusted while the torpedo was in the tube. Because of the lining in the tube, 450mm torpedoes had to be removed to change the depth-setting mechanism, and it certainly complicated matters when carrying a snap attack. One cannot minimise the importance of depth setting for oxygen torpedoes. A torpedo set shallowly increased the odds of hitting the target but at the cost of being sighted and allowing the target to take avoiding action in time. It also increased the risks that an escort, if present, would comb the tracks and carry out a deadly counterattack. A torpedo set too deep was less visible but might run under the target. At the same time, if attacking an armoured ship, it was important to set the torpedo deep enough so that it might strike under the armour belt.

The production shortage of the 533mm torpedoes may also explain the change in design brought by the submarines of the Cagni class. They were armed with a remarkable number of fourteen internal tubes, eight forward and six aft. All used the common 450mm torpedoes, and an extraordinary number of thirty-six were carried. This would have made them especially suited for ocean raiding, but by the end of 1941, the desperate supply situation in North Africa forced them to be used as transport submarines. Eventually, the only survivor of their class, Ammiraglio Cagni, reverted to her original role of an attack submarine after five supply missions to Bardia and Tripoli. The last submarine to join Betasom, her first raider mission lasted 138 days, the longest for an Italian submarine, but she only fired seven torpedoes. She was on her second raider mission in the Atlantic when she was ordered to interrupt it and bring back a cargo of rubber from Singapore. Cagni was in the Indian Ocean at the time of the Armistice, and her captain elected to surrender in Durban.

The shortage of torpedoes partly explains the lack of success of Italian submarines in the Mediterranean. Emptying all four forward tubes on a target rarely happened, and there was only one recorded instance in 1940 (Ascianghi on a large unidentified vessel on 22 June 1940) and only three in 1941. Usually, only two forward tubes were kept ready to fire, and firing a full salvo does not appear to have been part of the training, as the sudden discharge of several tons of ordnance required special efforts from the helmsman to prevent the submarine from popping up to the surface and be detected by the enemy. Yet an examination of British torpedo attacks shows that firing a salvo of four torpedoes was optimal, although the percentage of hits dropped off. It is true that British submarines were equipped with a system that partly compensated for the loss of weight and greatly facilitated the task of maintaining a specific depth.

However, at the Germans’ urging, Italian submarines began to use full salvos more regularly, and there were twelve instances in 1942 and nineteen in 1943⁴.

In 1942, a ‘senza bolla’ (trackless) apparatus, an invention of T.V. Aicardi, was fitted to the torpedo tubes. This was supposed to reduce the tell-tale bubbles visible when a torpedo was fired and encourage the firing of salvos. A torpedo-control firing system of German manufacture was also introduced on the new Tritone class submarines. This came too late; due to the deadly efficiency of the enemy’s anti-submarine tactics, submarines were now forced to fire at extreme range, and accuracy declined markedly. Less than three percent of torpedoes fired in 1943 hit their target. As early as August 1942, submarines were instructed to fire a maximum number of torpedoes at targets larger than torpedo boats⁵.

Another factor was that Italian submarines seldom operated in productive areas. Having learned to respect the anti-submarine capabilities of their adversaries, they were forced to act cautiously, which greatly reduced their achievements. Periscopes were used sparingly since listening equipment was more effective at a depth of 30 meters. This reliance on the hydrophones to detect the enemy certainly resulted in missed opportunities. Mediterranean acoustic conditions were inferior to that of the Atlantic due to the different layers of water temperature. To curb this excessive tendency, in January 1941, Maricosom felt obliged to order submarines operating in the Mediterranean to remain on the surface at least the first fifteen minutes of every hour during the night. In addition, there was a shortage of trained hydrophone operators. Although efforts were made to remedy this problem, submarines had to compete with the increased need of the surface fleet for their own anti-submarine fight. If they remained deepp for long periods to avoid detection, it was due to the belief that in the clear waters of the Mediterranean, a submarine could be seen by an aircraft even at a depth of 40 metres or more. This could be true, provided the aircraft flew directly above the submarine, but this was rare. Operating deep was not conducive to detecting the enemy, reducing their effectiveness.

MAIN TORPEDO TYPES USED BY ITALIAN SUBMARINES IN WW2
Type	Calibre (mm)	Length (m)	Explosive (kg)	Speed (kts)	Range (m)
W270, SI270 or SL2706	533.4	7.2	270	48	4,000
				38	10,000
W200, SI200 or SL200	450	5.75	170-200	44	3,000
				40	4,000
				30	8,000
W or A115	450	5.27	115	26	4,000

Gun Armament

Compared to other navies, Italian submarines had a good gun armament. Their large submarines were equipped with two 100mm or even 120mm guns, and the smaller submarines had a single 100mm. By contrast, large British submarines were mounted with a single 4in (102mm) gun and smaller submarines with a 3in (76mm) or 12-pdr gun.

The powerful gun armament encouraged Italian skippers to make surface attacks whenever possible, and they had several gun duels to their credit. Enemy merchant ships were usually armed and, on occasion, could put up a stout defence. Renowned commander Salvatore Todaro was perhaps the most prominent advocate of the gun as an offensive weapon. This brought the sardonic comment from Admiral Dönitz that he should have commanded a gunboat!

In a famous gun duel, the old submarine Enrico Toti (C.C. Bandino Bandini), armed with one 120mm gun, overcame the modern HMS Triad⁷. This was the only instance during this war when an Italian submarine sank an enemy submarine in the Mediterranean⁸. In another episode, Tazzoli (C.C. Vittore Raccanelli) was surprised by the British Talisman as she arrived at Bordeaux. She elected to submerge rather than fight it out, and her commander was severely criticised by Admiral Parona (head of Betasom) for not having used his superior firepower (two 120mm guns) to dispose of his adversary. In retrospect, this criticism appears to have been harsh; the Italian submarine had been surprised and was at a disadvantage as light conditions favoured his enemy. British submarines of the ‘T’ class could fire a tremendous torpedo salvo (ten from the forward and external tubes), and enemy submarines were considered targets warranting one. On this occasion, Talisman fired six torpedoes, one of which hit the Tazzoli but was a dud.

During the war, it was realised that the 120mm gun was unsuitable for the Atlantic theatre, as the shell was too heavy to handle in bad weather. These guns, as well as the older 102mm/35 calibre types, were progressively replaced on the Betasom submarines by the 100mm/47 calibre model. This move was not without its detractors. In a study submitted in 1942, C.F. Virgilio Spigai regretted that submarines were not armed with the older semi-automatic 102mm/45 calibre, which he found faster to load and more reliable.

Anti-aircraft armament was good, at least for the early part of the war, with up to four machine guns (13.2mm), usually of the Breda design, in twin mounts for large submarines. They proved their worth on more than one occasion, shooting down an attacking aircraft. This was necessary, as the large submarines were particularly slow in diving (90-120 seconds), making them vulnerable to enemy bombers, and they often elected to fight it out on the surface. On a few occasions, the main armament was brought to bear on the attacking aircraft, but this was more for intimidation purposes to allow the submarine time to submerge. Some of the German U-boats operating in the Mediterranean adopted the Breda machine guns.

By 1943, it became evident that machine guns were no longer sufficient to fend off modern aircraft. and a few commanders requested to have at least a single 20mm mount installed. This fell on deaf ears: only the large transport class submarines of the ‘R’ class were armed with three 20mm guns, which were their sole gun armament. Improvements were made with the new submarines of the Tritone class armed with one or two 20mm guns and able to dive in twenty-seven seconds. The ‘S’ class boats (German-built type VIIC) were completed with 20mm guns but were never operational beyond the training stage. In July 1943, Finzi and Bagnolini were finally equipped with a quadruple 20mm mount ceded by the BdU (Befehlshaber der Uboote or Commanding Officer Submarines), while Barbarigo and Torelli’s armament had been augmented by another twin Breda mount forward. Later, Italian submarines taken over by the Germans at Bordeaux were rearmed with 20mm and even 37mm antiaircraft guns.

The Italian submarine arm did not carry a single bombardment of enemy shores during the Second World War, despite doing several during the Spanish Civil War. When, in February 1942, Captain Polacchini (who had replaced Admiral Parona as head of Betasom) ordered two of his submarines to bombard American cities, the order was quickly countermanded by Admiral Legnani (the new head of Maricosom). The lack of bombardment in the Mediterranean Theatre was probably caused by a healthy respect for the RAF, an excessive fear of defensive minefields, and the vulnerability of the Italian coastline to retaliation. The Regia Marina made extensive use of defensive minefields; it assumed that the Royal Navy had heavily mined the Egyptian and Palestinian coasts, but this was not the case.

Mines

The three submarines of the Micca class were used to lay mines off Alexandria (twice), Ras Kenayis (off the Egyptian coast between Mersa Matruh and El Alamein), Jaffa, and Zante. A fourth submarine, the Bragadino, made the last mine-laying mission off Navarino on 29 October 1940 (the day following the Italian invasion of Greece). Two of these missions were interrupted when mines prematurely exploded, and there was no solid evidence that these minefields had achieved any result. It is probable that the mines used were unstable, and the loss of Foca (ca. 15 October 1940) may well have been accidental. A defensive minefield was laid by Atropo near Taranto at the end of December 1940, but this was more to test the process. The result must not have been satisfactory, as no more offensive minelaying missions were carried out during the remainder of the war.

The mines used, such as those of the P.150 type, could be laid in deep waters. Early in the war, the British recovered a mine laid off Alexandria. To their great surprise, they discovered it had been laid in waters as deep as 300 metres, whereas British mines were usually laid in less than 100 metres. However, laying mines at such depths required the use of thinner cables, which resulted in many Italian mines becoming detached in bad weather and being a threat to navigation. It may also explain the high incidence of Italian vessels lost near their defensive minefields. Yet the discovery had an unexpected benefit for the Italians, as British submarines were ordered not to operate in waters of less than 200 fathoms (360 metres) near the Italian coast unless an important target warranted the risk. This limited the efforts of British submarines for several months and partly explains their indifferent performance in the early months of the war.

The other submarines of the Bragadino class (Bragadino and Corridoni) and Sciesa of the Balilla class were theoretically able to lay mines, but only Bragadino was employed as such in a single mission. It was decided that the large minelaying submarines were better suited for transport missions.

After the Anglo-American landings in Morocco and Algeria, two former French submarines Saphir and Turquoise were incorporated in the Regia Marina. They were of a very successful design (their sister ship, the Free French Rubis, was one of the top minelaying submarines of the war), but adapting their minelaying tubes to use Italian mines would certainly have been a problem, and they were never commissioned in time. At the end of August 1943, Atropo was ordered to lay an experimental minefield near Taranto. This may have signalled a return to this type of operation, but the armistice intervened, and the surviving minelayers (Atropo and Zoea) were found to be more useful in transport or exercise roles.

Human torpedoes and midget submarines

Four submarines were adapted for the transport of human torpedoes to attack enemy harbours. The first operation, an attempt against Alexandria, started out badly when the Iride was sunk by British Swordfish torpedo bombers in the Gulf of Bomba on 22 August 1940. Five weeks later, another submarine, the Gondar, was intercepted and sunk before reaching the same target. But the most famous was undoubtedly Scirè. Ably commanded by Junio Valerio Borghese, she carried out three missions against Gibraltar, but her most successful mission was against Alexandria, where the last two remaining battleships of the Mediterranean Fleet were put out of commission on 18 December 1941. It was an extraordinary success that changed the naval power balance in the Mediterranean and helped the Axis drive, which was only stopped at El Alamein. Borghese, an unrepentant fascist⁹, is certainly one of the great Italian submarine commanders, even though he is not recorded to have fired a single torpedo in anger during the war. His weapon was the maiale or SLC¹⁰, and he exhibited great courage and navigational skills to attack the two strong points of the Royal Navy in the Mediterranean, Gibraltar, and Alexandria. Unfortunately, his submarine would be lost under a new commander, Bruno Zelik, while attacking Haifa the following summer.

The last surviving submarine, Ambra, carried out an unsuccessful attack against Alexandria on 14 May 1942. Success was achieved when frogmen (known as Gamma men) were used in an attack on Algiers on 11 December 1942. At the time of the armistice, Ambra was at La Spezia, unable to sail, and was scuttled.

In 1942 a fifth submarine, Leonardo Da Vinci, based at Betasom, was transformed to transport a midget submarine of the CA–class destined to attack New York harbour. The project was abandoned due to technical difficulties and she reverted to her original role of attack submarine. She would become the top scorer of Italian submarines before disappearing in the Atlantic Ocean in 1943.

In 1943, the newly built submarines Grongo, Murena, and Sparide were being adapted for use by the Decima Flottiglia MAS, but the Armistice intervened before they could be completed. They all fell into German hands, though none became operational.

Midget submarines were initially used in an anti-submarine role by patrolling off Salerno and Naples, but they never intercepted a British submarine. Six of them were sent to operate in the Black Sea, where they attacked three Soviet submarines and managed to sink one.

Detection apparatus and defensive measures

Submarines were equipped with hydrophones of the S.A.F.A.R.¹¹ or O.L.A.P.¹² type, with sixteen microphones reputedly effective to 15 to 20,000 meters under optimal conditions. Efficiency depended on the operator’s training and on the equipment itself. At the end of 1940, some equipment had not been fully tested in the rush to complete submarines. The S.A.F.A.R. hydrophones on Onice were found to be useless when the underwater speed exceeded 1.5 knots, and some parts had to be replaced. Active sonar was non-existent in the submarine arm of the Regia Marina. Developed by S.A.F.A.R., a variant was experimented early in 1940. Only the submarine chaser Albatros was equipped with it at the start of the war. From November 1941, Italian escort vessels were gradually being equipped with S-Gerät, a German variation of ASDIC. No attempt was made to adapt it to submarines, although British submarines used theirs with great results. This was probably influenced by the OKM (Oberkommando der Kriegsmarine or German Naval High Command) belief that S-Gerät emissions by U-boats might help escort vessels detect their position.

Submarines were also equipped with the Rovetto System which enabled them to maintain a specific depth when was stopped and made them less vulnerable to detection from hydrophones. Its major drawback was that it could only be used at shallow depths (usually about 30 metres), and the noise defeated its purpose. The ASDIC quickly negated its meagre advantages.

By the beginning of 1943, Italian submarines were being equipped with the German Metox, a primitive radar detector. It was useful in detecting approaching aircraft, although its warnings had to be ignored in areas of intense air traffic¹³.

Although the Italian Navy had experimented with a form of Schnorkel for underwater air intake as early as 1926, the project had been abandoned. The German design came too late in the war to be adopted by the Italians.

To confuse the Asdic, Pillenwerfer¹⁴ were also installed. They do not seem to have been used often. These appear to have initially been tested on the submarine Rismondo.

In July 1943, Menotti was equipped with Rari, a radar emission locator. This worked well during a special mission near Benghazi, but it came late in the war, and no other submarine appears to have used it.

A factor not often mentioned was the importance of binoculars used by the lookouts. Italian binoculars manufactured by Koritzka did not prove a great success and were often useless after a few days at sea. Surprisingly, navies of the Second World War did not make provisions for their submarines to carry more binoculars than they did, at least initially. After all, the item was relatively cheap, and the survival of the submarine could depend on it. This oversight was not limited to the Regia Marina, but to other navies as well, and at the beginning of the war, British submarines were issued with three or four pairs of binoculars only. Following the attack on the French fleet at Oran in July 1940, the Italian submarine Axum sailed for a patrol carrying only one pair of binoculars as the remaining three needed repairs and had to be left behind. Later, the German Zeiss binoculars were much sought after for the quality of their lenses¹⁵, but even they were not immune from humidity, and several spares had to be taken on long patrols. Soon, the Germans realised that their submarines needed extra pairs in a long patrol as humidity inevitably took its toll. After the first year of the war, U-boats were usually issued with sixteen pairs and sometimes even more. By August 1941, Maristat had issued directives that ocean-going submarines were to be equipped with fourteen pairs of binoculars (two German-made 7 x 50 Zeiss Septar, two Italian-made 7 x 50 Septar, and ten Koritska pairs) while coastal submarines would get ten pairs (two German-made 7 x 50 Zeiss Septar, two Italian-made 7 x 50 Septar, and six Koritska pairs). Should binoculars of the Septar type be unavailable, the ocean-going submarines would be equipped with twenty-two pairs and the coastal submarines with sixteen pairs of the Koritska type in tacit recognition that these were least resistant to the weather.

To combat Italian submarines, the main weapon used by the Royal Navy was the Mark VII depth charge which packed 300 pounds of amatol high explosive. It was expected to be lethal when detonating 25 feet from the submarine, although an explosion at 50 feet could inflict damage serious enough to force the submarine to the surface. There were six depth settings from 50 to 500 feet and the depth charge had a sinking rate of 10 feet per second. Since this was slow enough to allow the target to move away, an additional ballast of 140 pounds was added to increase the rate to 16 ½ feet per second. When it was realised that U-boats could dive deeper than British submarines, depth settings were increased to 550 feet and eventually to 850 feet¹⁶. On occasions, Italian submarines dived to 140 metres (approximately 450 feet), a depth rarely achieved by British submarines. Later, the Spigot Mortar (Hedgehog) and Squid were introduced as contact weapons, but there is no evidence that they were ever used to dispose of Italian submarines.

Intelligence, Communications, and Security

The Italian Intelligence Service or S.I.M. (for Servizio Informazioni Militare) could be relied upon to supply valuable warnings concerning Force H movements from agents at Algeciras, opposite Gibraltar. Monitoring the movements of the Mediterranean Fleet proved more difficult. This relied mainly on reconnaissance aircraft based in Libya or in the Dodecanese, and flights over Alexandria could not be maintained daily. The Japanese Military Attaché in Cairo tried to supply some information, but it came with little or no operational value. In any case, this source of information dried up with Japan’s entry into the war in December 1941.

The Italian Navy used a highly centralised communication system divided into areas all linked to Rome. These areas could not communicate directly among themselves, so they had to go through the Rome station¹⁷. Thus, Benghazi could not communicate with Athens without first passing the signal to Rome, which would then relay it. Most of the time, sailing orders to submarines were issued by Maricosom in Rome, but some of the submarine flotillas had a degree of autonomy. Thus, the Dodecanese and Massawa-based units and later the submarines of Betasom were usually controlled by their Grupsom.

When entirely submerged, Italian submarines could not communicate with their home base, nor could they communicate amongst themselves as their British counterparts could, by using their Asdic apparatus. Communications with their base was made on the surface or semi-submerged. However, they could receive signals at periscope depth, usually done every hour after listening with hydrophones. They used a medium and short wave set of the type S.I.T.I. (Società Industria Telefoniche Italiana). An important signal would be indicated by ‘Precendenza Assoluta’ or absolute precedence. A PAPA (Precedenza Assoluta sulla Precedenza Assoluta) signal indicated that it had the highest priority. The medium wavelength was usually used to communicate the time of arrival at the base, usually two to four hours before¹⁸. Italian ciphers used by the Regia Marina had been cracked by British cryptanalysts from the time of the Abyssinian Campaign. At the beginning of the war, signals were regularly intercepted, but it seems that few were deciphered due to a shortage of staff. The capture of the submarine Galileo Galilei off Aden on 20 June 1940, though a coup for British propaganda, was a serious setback for British Intelligence. Italian Naval Intelligence wrongly assumed that the codes had been captured, and a wholesale change in the code system brought this source of information to a stop. The Italian Naval Code system remained secure (the one used by the Regia Aeronautica was not) until pressure from the Germans forced them to use an Enigma-type cipher machine, the C-38 model, which proved to be as vulnerable to British experts as the German Enigma. Contrary to German U-boats, Italian submarines were discouraged from using their radio for security reasons. Supermarina issued a directive on 28 June 1940¹⁹, restricting the use of radio except in very serious circumstances. Betasom submarines were equipped with the Enigma coding machine in 1942.

Not many losses of Italian submarines can be directly attributed to Naval Intelligence; Galvani was lost in the Indian Ocean as papers collected on Galileo Galilei showed her patrol area. At the end of June 1940, the capture of papers from Console Generale Liuzzi revealed the position of a patrol line of four submarines between Derna and Gavdo Island. A destroyer sweep of the area netted one of the submarines (Uebi Scebeli), but she was not detected in the position listed in the captured documents. On 18 October 1940, papers were seized from the submarine Durbo near Alboran. Thanks to these, Lafolè was sunk two days later following a sweep by British destroyers.

An attempt to intercept the four submarines that had escaped from Massawa in the spring of 1941 failed, although signals had been deciphered, giving their refuelling points. The narrative will examine this in detail.

There were very few intercepts of signals from Italian submarines because, very prudently, they kept their communications to a minimum. Most intercepts were from their Grupsom (Flotilla) commands, which usually indicated the departure and arrival of submarines. Those came mostly from outside Italy, such as the Leros-based submarines or Libyan traffic. On mainland Italy, most commands could be delivered by telex and were less susceptible to enemy intercept efforts.

At the start of the war, the Regia Marina Cryptographic Bureau was headed by Capitano di Fregata Gino Cianchi. This service succeeded in breaking several British Naval codes, including the Fleet code, though it was often too late to be of operational value. The Regia Aeronautica did not have a cryptographic service, and the work was also done by the Regia Marina Bureau. The RAF’s high-level code was not broken, but common RAF messages were frequently read. Co-operation with the Germans was good, although the latter did not disclose their full knowledge of British signals for fear that this would become known through an Italian leak.

Naval Grid System

Italian submarines used a grid chart system similar to the ones used by the Royal Navy and Kriegsmarine. The Germans briefly used a simplified system in September 1939, before switching to the standard one used for the remainder of the war. Curiously, they never needed to change the grid chart system, even though capturing a U-boat such as U-570 and other vessels could have provided the enemy with copies of these maps. The Regia Marina used two different grid chart systems, one for the Mediterranean and one for the Atlantic and Indian Oceans. The position was expressed by a four-digit number, quadratino or quadrant, the first two digits representing the latitude and the next two digits the longitude. This was very similar to the Royal Navy grid system with its two pairs of letters instead of digits. Maps were provided, giving the two-digit equivalent for each degree. However, whereas the Mediterranean grid divided the map into main quadrants 20’ x 20’, the Atlantic system divided the map into quadrants, each representing one degree or 60 minutes. For more precision, a sottoquadratino or sub-quadrant was also provided, and again, the Atlantic system differed from the Mediterranean one. The Mediterranean grid had a single-digit system for the sub-quadrant, which divided a square degree into six parts numbered 1 to 6 (boxes of 10 minutes wide for longitude and 06’40” tall for latitude).

Example: on the map, each degree was represented by a two-digit number. For example, 32 might represent the latitude between 35°20’ North and 35°40’ North. Another two-digit number, such as 47, might represent the longitude between 15°20’ East and 15°40’ East. Quadratino 3247 with sottoquadratino 4 would thus represent 35°30’ N, 15°35’ E. Substituting to these, the sottoquadratino 5, would represent 35°23’20” N, 15°25’E (the centre of the square being used as reference). To make it more difficult for the enemy to decipher, two alternate sets of two-digit numbers could be used for the latitude in the main quadrant.

In the Atlantic System, the two-digit system was used for both degrees of latitude and longitude, but the square degree was divided into 36 boxes (6 x 6), dividing degrees both in longitude and latitude in sections of 10 minutes each. No substitute numbers were used for latitude, as in the Mediterranean. The sottoquadratino was expressed in a two-digit number, each digit numbered from 1 to 6. For example, in a sottoquadratino of 41, 4 meant 35 minutes west, and 1 meant 5 minutes north (the middle of that square in both cases). In the quadratino 9039 with a sottoquadratino of 35, where 90= 36° N and 39 = 15° W gave a position of 36°45’ N, 15°25’ W.

To make it more difficult to decipher, the sottoquadratino could alternately be changed to the following:

This time the sottoquadratino of 35 indicated a position of 36°25’ N, 15°45’ W.

These charts could be in effect for varying periods, sometimes for two months or more in the Atlantic. For the Mediterranean, it could be as short as five to seven days. This made the Italian grid chart system quite secure. British Intelligence appears to have had some success in decoding it, especially after the landings in North Africa, but it is not clear if this was due to the capture of charts or to the deduction of the large volumes of deciphered signals.

In addition, the use of code names for specific positions, a practice especially in use in the Mediterranean Theatre, made them fairly immune to Allied inroads in their cipher systems. The patrol positions in the Eastern Mediterranean were frequently broadcast without using the Quadratino, although British Intelligence does not appear to have much benefit from it. Finally, for added security, a two-digit number square system, allocated to specific operation zones only, was used on the eve of the invasion of Sicily. It was also common for Maricosom to send signals to fictitious submarines to confuse Allied Intelligence, but the stratagem was discovered with the capture of Bronzo and her log signals in July 1943.

Submarines in anti-submarine role

Italian submarines were often used in defensive patrols off their bases. These patrols were generally passive, as the submarine would lie on the bottom for a hydrophone watch. The objective was to intercept enemy submarines believed to be lurking near Italian harbours. These short patrols were usually carried out from nightfall to dawn when the submarine would return to harbour. Such missions were considered necessary after the shelling of Genoa by Force H in February 1941. It had proven the vulnerability of Italian bases, as the Regia Aeronautica had failed to provide adequate warnings. Ultimately, they proved disappointing; enemy submarine contacts were extremely rare, and none were sunk. Even the newly-built midget submarines (Caproni or C.B. boats) were used for this role. Initially, they carried out anti-submarine patrols in the Salerno area, which was recognised as particularly suitable for enemy commando raids, and prophesied the actual Allied landings of 1943 in the very same area. They were later transferred to the Black Sea, and one succeeded in this role by sinking a Soviet submarine. HMS Triad was the only British submarine sunk by an Italian counterpart in a celebrated gun duel, but the encounter had been fortuitous.

These patrols were not limited to Italian ports. In September 1941, Onice was sent to Benghazi where she carried out twenty-five nightly patrols, mostly independently, although a few were combined with torpedo boats or patrol vessels. HMS Thrasher was sighted on the night of 25/26 September, but Onice could not get into an attacking position.

Transport submarines

Submarines were employed for nearly 170 transport missions. In the Mediterranean, they were needed for transport missions to Libya, the Dodecanese islands (until the Greek surrender), Tunisia, and isolated islands such as Pantelleria and Lampedusa.

Admiral Domenico Cavagnari, Under-Secretary of State for the Navy, in a pre-war examination of a possible war with Great Britain, envisaged their use to supply Libya as a way to circumvent a superior Royal Navy. He appeared to have greatly underestimated the needs of the Italian army in this theatre. He suggested that submarines could bring 500 to 600 tons of supplies monthly, which would be enough to sustain them. In fact, the daily requirement for an Italian division was about 300 tons. The primary mission of the Regia Marina was to ensure that the lines of communications with Libya and the Dodecanese were kept open. Later, the invasion of Greece added new burdens as the Italian Fleet had to keep steady supplies for the Army in this theatre.

The large submarine Zoea carried out the first supply mission, and brought forty-nine tons of ammunition to Tobruk on 21 June 1940, while her sister ship Atropo brought supplies to Leros on 26 June. After July 1940, the use of transport submarines was temporarily halted as the threat of the Royal Navy on Italian communications with Africa appeared to have receded, and freighters were used instead. Their use was briefly resurrected in March and April 1941 to bring supplies to the Dodecanese islands, which were isolated by the war with Greece. With the fall of Greece, the focus reverted to Africa, and from May 1941, they were used to transport supplies to Derna and later to Bardia and Tobruk for Italian forces as well as the German Afrikakorps. As Axis fortunes ebbed in North Africa, transport missions were carried out to Benghazi and then to Tripoli. Through ULTRA, the British understood these submarines were making landfall at Ras Hallab (30 miles east of Tripoli) and then were led by a patrol vessel through the minefields to Tripoli. Curiously, they failed to take advantage of it. Perhaps they gave priority to the larger transports. Finally, a couple of missions were carried out to the Tunisian ports as well as the islands of Pantelleria and Lampedusa, which were now isolated because of Allied naval and air superiority.

Although submarines had a small cargo capacity, usually less than 100 tons, they were used extensively in this role. During the summer of 1942, as Axis forces struggled to gain the upper hand in North Africa, most of the supplies were forwarded to Tobruk. Submarines could bring supplies quickly as most of the merchant ships had to go through the Corinth Canal to avoid the RAF. At Tobruk, about a hundred F-lighters (two-thirds of them Italian-built) were used at one time or another to ferry supplies to Mersa Matruh, the harbour closest to the front line. Submarines never went as far as Mersa Matruh as a single F-lighter could deliver about the same load of stores. The lighters had poor sea-keeping qualities and could not replace the submarine completely, but they were more adapted to coastal traffic and cheaper to produce.

In the Spring of 1943, Admiral Dönitz, conscious of the increasing need for rubber and other materials from the Far East, proposed to take over the large surviving submarines at Betasom and use them as transports in exchange for an equivalent number of type VIIC submarines. This was accepted and Italian crews began to take over German U-boats, and the Betasom submarines were sailed for the Far East. The large submarine Ammiraglio Cagni was the last westbound Axis submarine to cross the Straits of Gibraltar, and on her second Atlantic cruise, she was ordered to the Far East to bring back a cargo of rubber. The armistice found her in the middle of the Indian Ocean, and her crew elected to join the Allies. The need for transport submarines was such that the Germans also asked the Italians to contribute some of their large Mediterranean submarines. This was nominally accepted, provided that the German submarines to be exchanged were delivered to an Italian port before the transport submarines could be made available. The Armistice prevented this from occurring.

A remarkable new design, the ‘R’ class, addressed the need for transport submarines that could carry 610 tons of stores. Despite their size, they had a small conning tower, reflecting the need to evade enemy radar. Unfortunately, the two that were completed, Romolo and Remo, were lost early during the invasion of Sicily as they were being moved from Taranto to Naples. None of the other units of their class were completed after the Armistice²⁰.

Following the Armistice, the Allies used a few Italian submarines to supply the garrisons of Leros and Castellorizo before these islands fell to German hands.

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1. See La Marina Militare nella Seconda Guerra Mondiale (USMM), «L’organizzazione dell marina durante il conflitto », Vol. XXI (T.1), Rome, 1972. ↩︎
2. With an exchange rate of 60 Lires to the British Pound at the start of the war, this meant a cost of respectively 1,000 and 5,000 GBP. ↩︎
3. There is evidence that this was later increased on some submarines of Betasom to two tubes forward and two aft. ↩︎
4. Interestingly, the British similarly urged their Russian allies to fire salvoes at targets, as the latter had encountered little success by often firing single torpedoes. ↩︎
5. See the signal in the Dagabur file. ↩︎
6. The W suffix indicated a torpedo manufactured at Siluricio Whitehead of Fiume (the oldest manufacturer of torpedoes, since 1861). SI indicated Siluricio Italiano of Naples, and SL indicated Siluricio Motofides of Leghorn. Note: siluro is the Italian word for torpedo. ↩︎
7. There has always been an element of doubt as to the identity of the British submarine. Some sources have suggested that the submarine sunk was HMS Rainbow. Although the possibility exists, it is almost certain that Triad was the one encountered and sunk. Rainbow‘s position was farther away, and she should have vacated it the previous night (see the paper by Robert M. Coppock of the Naval Historical Branch). ↩︎
8. One must add that the midget submarine C.B.4 almost certainly sank the Soviet submarine SC-203, but this was in the Black Sea. ↩︎
9. Nicknamed the ‘Black Prince’; he attempted a coup d’état in 1970 but was forced to flee to Spain. ↩︎
10. Siluri a lenta corsa or slow-speed torpedoes, also known as maiali (‘pigs’), because early attempts had found them unreliable and the name stuck. ↩︎
11. Societa Anonima Fabbrica Apparecchi Radio-Acoustici, Milano. ↩︎
12. Officine Lombarde Apparecchi Precisione. ↩︎
13. On 15 August 1943, the German Naval High Command forbade the use of Metox with the mistaken belief that its emissions were used by enemy aircraft to home on U-boats (DEFE3/332/page 36, TNA). ↩︎
14. An Asdic decoy, the Pillenwerfer (‘Pill thrower’) or Bold, was a canister filled with calcium hydride, which released bubbles to give false echos. ↩︎
15. British submariners would admit that they were better than their own. ↩︎
16. Cf. ADM1/19150 (TNA). ↩︎
17. Cf. GCHQ Official Histories Vol. XVI: The Italian Navy by Dorothy Atkinson, Lieutenant A E H Frost, RNVR and Lieutenant R R Thornton, RNVR; edited by Commander A M S MacKenzie, RNVR in HW11/29 (TNA). ↩︎
18. Cf. Argomento: Norme per l’impiego dei sommergibili in guerra by Admiral Falangola, a copy of it with its English translation can be found in ADM223/74 (TNA). ↩︎
19. Cf. Argomento: Uso della radiotelegrafia in Maricosom Cartella 24 (USMM). ↩︎
20. The conning tower of R.12 is preserved at the Caserna Angelo Paolucci in Rome (which is also the home of the Ufficio Storico della Marina Militare). ↩︎