Statistics

Operations, Tactics, and Statistics

Italian submarines were faced with two different types of war. In the Mediterranean, they often travelled to their patrol positions and operated in a static role. Usually, listening to their hydrophones at a depth of about 30 meters and return to the surface every hour to have a quick look with the periscope and listen to their radio. Maricosom preferred to keep a reserve of submarines available for operations on short notice rather than maintaining the maximum number of patrols possible. Warships were the preferred targets, and there was no tonnage warfare as advocated by Dönitz for the Atlantic. Merchant ships were specifically targeted in the summer of 1942, when neutralising Malta became paramount.

In the Atlantic, Italian submarines experienced difficulties in attacking convoys. Their massive conning tower, which was conspicuous, often prevented them from closing to the attack. Lack of training would soon become apparent. Dönitz preferred to send them away from the convoy lanes where they could prey on isolated ships. Italian submarines from Betasom roamed the Atlantic on the surface; if a ship or convoy was sighted during daylight, the tactic was to take a parallel course and then close to intercept after darkness. To succeed, the submarine commander had to learn to evaluate the enemy’s course and speed correctly. Italian submarines were handicapped as their maximum speed was a couple of knots inferior to German U-boats. This may not seem much, but in a chase of ten hours, this represented twenty nautical miles and could make a massive difference in its outcome. As they were moved away from the convoy lanes, many lengthy chases only ended up with disappointment as the vessel hunted often proved neutral, mainly Spanish and Portuguese, making a brisk trade with Latin America.

Like most submarines of their time, Italian submarines could not fire a salvo greater than four torpedoes. American submarines could fire salvoes of six torpedoes, and the early group of the remarkable British T-class submarines could even fire ten¹. In theory, the Ammiraglio Cagni class could have fired eight, but they never fired more than a salvo of three in operation. As shown in Table 1, by the end of the war, a complete change in the pattern had occurred, with most attacks being carried out with full salvos instead of the single torpedo attacks, which had been the norm in 1940.

British submarines usually carried out a full complement of torpedoes, and full salvos were often used from the start of the war, except when the target size did not warrant such expenditure. The torpedo shortage was not a serious problem in the Mediterranean except for a brief period following the sinking of the submarine depot ship HMS Medway in June 1942. Despite the shortage brought by the siege, most Malta-based submarines usually sailed with a full load, although torpedoes had to be borrowed from the destroyer depot for some time. However, submarines leaving Malta for the United Kingdom or returning from a supply mission were often armed with only two torpedoes so as not to deplete the stocks on this island.

Italian submarine torpedo attacks in the Mediterranean
Number of torpedoes fired	1940	1941	1942	1943	Total
1	57	242	173	4	102
2	19	22	24	8	74
3	3	7	12	5	29
4	1	3	14	19	36
Torpedoes fired	106 (93)	101 (100)	157 (132)	107 (102)	471 (427)
Torpedo hits	12 (11.32%)	5 (4.95%)	14 (8.92%)	3 (2.80%)	34 (7.22%)
Number of attacks	58 (52)	40 (40)	52 (50)	33 (31)	183 (173)
Torpedoes fired (Monthly avg.)4	15.89	8.42	13.08	12.97	12.10
British torp. fired (Monthly avg.)	22.35	61.17	71.17	126.40	62.42

Italian submarine torpedo attacks outside the Mediterranean
Number of torpedoes fired	1940	1941	1942	1943	Total
1	575	94	68	12	209
2	14	29	69	10	106
3	1	2	2	4	9
4	0	2	2	1	6
Torpedoes fired	88	166	223	61	538
Torpedo hits	24 (27.27%)	54 (32.53%)	94 (42.15%)	22 (36.07%)	194 (36.06%)
Number of attacks	45	64	74	25	208
Torpedoes fired (Monthly avg.)6	13.20	13.83	18.58	7.39	13.82

Chart 1 – Statistics of Italian torpedo attacks in the Mediterranean. After the initial peak at the start of the war, we can observe other peaks during Operation PEDESTAL (August 1942), the Anglo-American landings in North Africa (November 1942), the increased use of full salvo firing (January 1943), and the invasion in Sicily (July 1943).

Chart 2 – Statistics of Italian torpedo attacks in the Atlantic. Note the peak in December 1940 when Betasom was at its greater strength before winter set in. The renewal effort was in the spring and summer of 1941 when several submarines were recalled home, and finally, a peak was in March 1942 during Operation PAUKENSCHLAG.

The sudden drop in Italian submarine attacks in 1941 is partly due to the departure of twenty-seven submarines for the Atlantic theatre and the loss of fifteen submarines in the Mediterranean by the end of 1940. Thus, at the beginning of 1941, the Italian Submarine Fleet could deploy only sixty percent of the boats available at the beginning of the war in the Mediterranean. Undoubtedly, the severe losses that occurred right at the beginning of the war had a sobering effect on Maricosom’s activities, which were reduced accordingly for conservation purposes. Ten submarines were lost in the first three weeks of the war; this was an unsustainable attrition rate. On the other hand, early in 1941, the British submarine fleet increased with the arrival of the new U-class submarines based in Malta and were never short of targets. Italy depended heavily on her sea communications, and with 2,200 km of coastline to defend, mounting an effective anti-submarine defence proved insurmountable. In addition, the Regia Marina had the additional task of providing escorts to the numerous convoys plying the routes to Libya. With the occupation of Greece, it was further burdened with supplying the Italian and German garrisons stationed there.

The Asdic threat was well known; however, its effectiveness remained a mystery as Italian submarines sunk by British anti-submarine forces could not tell the tale of their destruction. Although the French Navy was equipped with Asdic, the Armistice did not appear to encourage cooperation with the Italian Navy. At the beginning of the war, the Regia Marina had only one experimental destroyer suitable for anti-submarine warfare, the submarine chaser Albatros, which was fitted with experimental Asdic (SAFAR P 600).

Most information on its detection capacity appears to have come from pre-war conversations with British Naval personnel. Undoubtedly, this significantly contributed to the prudence exhibited by Italian submariners. Yet British anti-submarine warfare experts did not consider Asdic conditions in the Mediterranean as good as in the Atlantic. Still, the excellent weather and the clear waters of the Mediterranean made submarine attacks more difficult. Torpedo tracks could sometimes be seen as far as 2,000 metres away, allowing the target to take evasive action. In fair weather, this made submarines very cautious in their attacks. Every attack brought the fear of retaliation from the escort; the destroyer could comb the torpedo track and deliver a deadly depth charge attack.

The German Navy had partly solved the problem with the electric torpedo. It left no track and thus gave relative immunity to the attacker. However, it would take two years before Italian submarines were similarly equipped, and by this time, enemy forces had perfected their anti-submarine tactics, nullifying this advantage.

Night attacks were thus favoured because of the greater chance of achieving success and allowing the attacking submarine to escape. Since targets were often escorted in the Mediterranean Theatre, submarines seldom remained at periscope depth to observe the result of their attack. This caution was not limited to Italian submariners alone; the British ace David Wanklyn of Upholder did not observe the result of his attacks before the sinking of the submarine Ammiraglio St. Bon in January 1942, a full year after intensive service in the Mediterranean. In most instances, Italian commanders relied on their hydrophones, frequently mistaking the sound of explosions (often caused by depth charges, premature torpedo explosions, etc.) for torpedo hits and making claims that were not substantiated.

Italian Naval Intelligence obtained good information on Gibraltar from agents operating across the bay from Algeciras. This was not the case for Malta and Alexandria, which mainly relied on occasional and imperfect aerial photographs. They managed to intercept and decipher some of the signals used by RAF bombers, and information was also obtained from the German B-Dienst, but very parsimoniously.

Italian submarines achieved their best results in the Atlantic, where, at first, anti-submarine tactics were still primitive and escorts few in number, and later, they operated in areas where they could attack unescorted ships. Whereas Mediterranean submarines averaged less than eight percent of torpedo hits, Atlantic submarines achieved a very credible thirty-six percent, and this was undoubtedly boosted by the ability of the Betasom submarines to conduct repeated attacks on a lone victim. At the same time, their Mediterranean counterparts were more often reduced to hit-and-run tactics. By contrast, during the war in the Mediterranean, British submarines obtained about seventeen percent of hits from torpedoes fired and German U-boats twelve percent (up to 8 September 1943). These percentages are calculated on a minimum of confirmed rather than claimed hits, and the actual figures may have been slightly higher.

As Allied anti-submarine tactics improved, Italian submarines in the Mediterranean reached their low point in 1943, with less than three percent of torpedo hits. Even the arrival of new submarines and the use of electric torpedoes could not stem the tide.

A significant problem for Italian submarines was the scarcity of targets, as the traffic between Gibraltar, Malta, and Alexandria was occasional. The few convoys were fast and heavily escorted. Early Italian doctrine had advocated using submarines in conjunction with surface fleet operations, a task for which their slow speed made them ill-suited. Submarines were often deployed at a healthy distance from the enemy naval bases, making the interception of enemy units more of a question of chance. This was brought about by very effective anti-submarine patrols carried out by the RAF and Coastal Command. Italian and German aircraft, though often used to cover Axis convoys, rarely presented a threat to Allied submarines, and their attacks were remarkably few. British aircraft often carried depth charges and the use of radar and Leigh light, making their attacks more lethal. By mid-1942, Axis submarines could no longer use the dark hours to recharge their batteries safely.

It is perhaps significant that there is no absolute certainty that Axis aircraft ever sank an Allied submarine at sea in the Mediterranean during the war. The three submarines that were victims of the Axis bombing were all sunk in their Malta anchorage. A German bomber may have sunk HMS Turbulent south of Capri in March 1943, but there is no absolute certainty. The claim that HMS Urge was sunk by a CR.42 fighter was proven wrong when her wreck was found off Malta in 2019; she had been the victim of a mine.

Italian submarine losses from all causes (up to 8 Sept 1943)
Cause	Lost	Note
Surface craft	41.5	Including two captured and three (1.5) shared with aircraft.
Submarine	18	Including one sunk in error (Gemma) and one torpedoed by a Dutch submarine.
Air attack	13	Eleven plus three (1.5) shared with surface craft and one later scuttled (0.5).
Unknown	12	Includes a submarine sunk shortly after the Armistice (Topazio), one formerly attributed to a submarine (Acciaio), and another to an aircraft (Romolo).
Accident	4	Macallè (15 June 1940), Zoea (22 October 1941, later raised), Delfino (23 March 1943), and Aradam (23 July 1943, later raised).
Scuttled	2.5	Two ex-French submarines were scuttled in Bizerta, and Sciesa was scuttled in Tobruk following bomb damage.
Total	91	This includes one that was raised and returned to service (Zoea) and another being repaired (Aradam).

Table 3 – Submarine losses (up to the Armistice).

Of the submarines lost through unknown causes, one loss appears to have been accidental (Foca), and most others appear to have been caused by aircraft, but we cannot be absolutely sure. The high numbers of submarines sunk by their British and Dutch counterparts can be explained by two important factors:

• Asdic was a tremendous advantage that favoured Allied submarines over Axis submarines. The Germans had reached the wrong conclusion that submarines should not be equipped with S-Gerät (the German Asdic equivalent) as they believed that the emissions would help anti-submarine forces locate submarines. No German or Italian submarines were thus equipped, by contrast Allied submarines made judicious use by using it in both passive and active mode. Asdic could not only detect the enemy but was instrumental in plotting the course and speed of the target. Asdic was not very effective on the surface, but radar, introduced on submarines later in the war, would give them another advantage. However, it does not appear to have been much used in detecting Italian submarines. Radar was most effectively used by surface craft and Allied bombers.
• During daylight hours, Italian submarines travelled on the surface in home waters as the Regia Aeronautica and the Luftwaffe had orders not to attack surfaced submarines. This made them especially vulnerable to British submarines since, to conserve fuel, they seldom proceeded at a speed of over 9-10 knots. They also frequently travelled on the surface to their operation area during daylight hours. Overall, Italian submarines travelled on the surface 96.6% of the distance covered, 3.4% submerged. This was almost identical whether in the Atlantic or Mediterranean Theatre.

General Overview of Operations

In the Mediterranean, Italian submarines were used to intercept traffic with Malta. As convoys to supply the beleaguered island were few, their opportunities were rare. Italian patrols were, on average, much shorter than those of German or Allied submarines, although mechanical defects played a role in some cases just as they did for other navies. Patrols of Italian submarines in the Mediterranean were frequently of short duration (less than a week), and patrols of German and Allied submarines usually lasted between two to four weeks. This problem did not affect Italian submarines operating in the Atlantic, where patrols often lasted five to six weeks.

The only logical explanation was that Maricosom was saving its strength for the coming critical battles and preferred keeping its submarines in port, available at short notice. This appeared justified when, in June and August 1942, Italian submarines operating against the VIGOROUS and PEDESTAL convoys outnumbered their German counterparts. However, this did not work well when Force H conducted frequent forays in the western Mediterranean to launch aircraft reinforcements for Malta; Italian submarines were rarely in position to intercept as they were too slow to react.

In the Mediterranean, German U-boats eclipsed their Italian counterparts in achievement. From September 1941 to the Italian Armistice, they fired 1,190 torpedoes, achieving 146 hits (12.27%) with 600,000 tons of shipping sunk or damaged. During the same period, Italian submarines fired 283 torpedoes, with 19 hits (6.71%) and less than 80,000 tons of shipping sunk or damaged. This is even though German U-boats never outnumbered their Axis partner in this theater. These figures do not include the successes of the Decima Flottiglia MAS, which outperformed the regular submarine arm and accounted for nearly 100,000 tons of shipping.

During the war, Italian submarines sank or damaged 120,000 tons of shipping in the Mediterranean; the Decima Flottiglia MAS added another 140,000 tons. By contrast, in the Atlantic and Indian Ocean Theatres, a small number of Italian submarines sank or damaged 600,000 tons of shipping, and the Red Sea and Black Sea submarines added another 13,000 tons.

The fuel problem that afflicted Italian surface ships throughout the war was not a factor in curtailing Italian submarine operations; the supply of diesel oil was always sufficient, and consumption was relatively small. Italian escort vessels were very active and proved indefatigable in their efforts to keep lines of communication open with North Africa.

Submarine deployment from 10 June 1940 to 8 September 1943
Theatre	Average patrol length (days)	Average number at sea	Torpedoes expended
Italian submarines
Mediterranean	6	10	477
Atlantic	30+	5.8	491
German submarines (from 21 September 1941)
Mediterranean	16+	7	1,190
British submarines
Mediterranean	12.8	9	2,519

(Numbers are subject to minor corrections)

---

1. T-class submarines fired a ten-torpedo salvo on three occasions, all during the Norway campaign of 1940. ↩︎
2. Including one accidental firing. ↩︎
3. Including seven torpedoes discharged accidentally or for safety reasons. ↩︎
4. The average is calculated based on 6 ^2/₃ months for 1940 and 8 ¼ months for 1943. ↩︎
5. Including one accidental firing. ↩︎
6. The average is calculated based on 6 ^2/₃ months for 1940 and 8 ¼ months for 1943. ↩︎