Why didn't Italian submarines surround Malta?

[Dili]

Italian submarines - the 600t class- also had only 4 bow torpedoes and no reloads - until the Acciaio class with 2 bow reloads. So the cpt would not launch spreads often - Axum did it in Pedestal hitting 3 ships .

[Platon Alexiades]

As Lorenzo Colombo alluded in an earlier post, Italian doctrine favoured firing only one or two torpedoes as production of 533mm torpedoes was insufficient (resulting in one forward tube adapted to fire 450mm torpedoes and no reserve torpedoes carried) and British convoys to Malta were usually formed by fast ships usually heavily escorted making them difficult to hit.

Another factor was a heavy reliance on hydrophones to detect the enemy and underwater sound conditions were not the best in the Mediterranean. If periscopes would have been used more often, British vessels would have probably been detected more often.

The loss of ten Italian submarines in less than a month after the war was declared was a shock and Maricosom concluded that the Mediterranean Theatre was not favourable to submarine operations (the Atlantic Theatre yielded much better results for the Betasom submarines). Oil shortage was probably another factor as Italian submarine patrols were usually short, an average of 6 days at sea, versus 16 days for German U-boats in the Med. This resulted in the Regia Marina maintaining for the period of 10 June 1940 to 8 September 1943, a daily average of ten submarines at sea. By contrast the German Navy with a much smaller number of submarines maintained an average of seven U-boats at sea in the Med for the period 21 September 1941 [when the first U-boat (U 371) entered the Med, I do not count the earlier foray by U 26] to 8 September 1943. To be fair, it was not a shortcoming in Italian submarine design as some of the submarines occasionally carried out patrols of 20 days or more but a fair number of patrols were of a defensive nature (especially after the bombardment of Genoa in February 1941) whereas German U-boats were only used in offensive patrols. Certainly, German U-boats were of a better design and since a number of days was usually required to reach the patrol positions, this meant they had a decidedly greater advantage and ended up firing more than twice the number of torpedoes as Italian submarines.

Maricosom did not establish a standing patrol near Malta, Gibraltar or Alexandria, preferring to send the submarines at sea only after it was informed that an enemy force was on its way to Malta. This meant that often the submarine deployment was too slow to react to the threat. Although, Italian Naval Intelligence was usually well informed of the departure of British vessels from Gibraltar by their agents at Algeciras, submarines based at Cagliari or elsewhere did not have sufficient time to intercept, in most cases Force H had already turned back after flying off Hurricane or Spitfire fighters.

I hope this helps.

Platon Alexiades

[Wargames]

Thank you! No reloads? I don't suppose you know their 21" torpedo production?

[Platon Alexiades]

The Official History (Vol. XXI: L'organizzazione della Marina Durante il Conflitto" just mentions a monthly production of 50 torpedoes in 1940 but does not specify if this was increased during the war.

[Wargames]

Thanks!

[Felix C]

Picket lines do not work and as mentioned traffic was too irregular. The area with constant traffic would be the Eastern Med. I would be interested in hearing about Italian submarines deployed to work between Cyprus and Egypt, Palestine, etc. trade routes. How often or if that was a German zone?

[Platon Alexiades]

Italian submarines based at Leros operated from Cyrenaica to the Levant. However, when German submarines started operating in these areas in the autumn of 1941, operation areas were specifically delimited between the Axis partners (these changed according to the needs of the time) and they never operated together.

[Urmel]

Coming back to the original question, I am not sure why you think they didn't? Or why somebody else takes the view that picket lines were inefficient?

[Platon Alexiades]

The Italian Navy had a healthy respect for the British A/S measures and methods (Asdic, A/S aircraft and later radar-equipped aircraft) and operating near Malta (Gibraltar, Alexandria, Haifa or other ports) was considered quite dangerous and not worth the risks involved. When Malta was practically neutralised during the Spring and Summer of 1942 then submarines could get closer (as shown on your maps) but even then there was more danger of Axis minefields which were numerous in the Maltese waters, especially those laid by the 3rd Schnellbootflottille in the Winter and Spring of 1942. Even the knowledge of the positions of these minefields was not enough as navigation in those days was not always very precise and dependent on good weather. Submarines sometime had to navigate by dead reckoning and an error in position from 10 to 15 miles was not rare.

[Urmel]

Sure. All I am noting is that they did sometimes surround Malta and established picket lines across Royal Navy supply routes. Which is addressing the original question.

[Felix C]

I am that "Someone else" Urmel, Picket line not useful as it was shown in WW1 that submarines were efficient when operating on ship routes, merchant and naval and not when posted away from known traffic routes. That would make the regular traffic from Cyprus, Haifa, Egypt liable to interdiction. Later Beirut after Vichy French Levant occupied.
Given the very infrequent British use of merchant traffic bound for Malta, submarines picketed there would be useless unless a transport run was known. Submarines wear out and require refit between patrols, the more service use the more lengthy the refit time. The two maps you show confirm that assessment as they are for when a British supply run was on for Malta. Post one when there was no traffic bound and it would be much less submarines unless it was as an anti-submarine picket out side of Malta to catch Allied submarines there which would not require many submarines on station in a crowded area to avoid friendly fire.

[Urmel]

Permanent picket lines, sure. But they clearly did put picket lines in place when they knew something was coming, same as the Royal Navy.

[Dili]

Thank you! No reloads? I don't suppose you know their 21" torpedo production?

There were enough 533mm torpedoes at war start but the allowance margin wasn't big.
Prod went from 46 in April 40 to 150 in April 43. But torpedo production wasn't an issue except in certain periods for aerial ones. Also there wasn't that many Royal Navy ships in Med. Only bursts of activity.
The use of 450mm with subcaliber tubes inside ones were due mostly to a "waste" doctrine of not wasting more expensive torpedoes into merchants.
That is why the biggest oceanic submarines for trade interdiction of Cagni class had only 450mm tubes with 14 tubes(8+6) one of biggest number of tubes in a submarine - in RM theory merchants did not warranted a 533mm one.

[Platon Alexiades]

Wargames wrote:
It was normal to employ 10 Italian submarines in the western Mediterranean versus Gibraltar (up to 20 versus Alexandria). The 10 subs were pretty useless not only because Somerville seldom showed but, when he did, he'd usually cheat the international rules of war and sail through French waters at night (The Italians obeyed international law and stayed out of French waters until Pedestal.). By passing through French waters at night the French were left unaware their waters had even been violated.
I think you are misinformed: Somerville did not usually cheat international rules. He usually kept at a fair distance from the French North Africa coast (about 50-70 miles). To hug the North African coast would have been very risky as if sighted, the French authorities would certainly have reported it immediately to the Italians and compromised their operation. The threat of the Italian Air Force and Italian submarines forced Somerville to fly off Hurricanes and Spitfires at a long distance from Malta causing several aircraft to be lost. However, because of a lack of standing patrol in Western Mediterranean, the sailing of submarines from Cagliari usually came too late to interfere with the launching of the aircraft and by the time submarines arrived on the scene, Force H had turned back. It is true that British blockade runners briefly used French waters but that was near Cape Bon (Tunisia) as they suspected (rightly) that the area was heavily mined except for French waters. HMS Havock violated French waters in April 1942 and as a result ran aground and was lost near Ras El Mihr (Tunisia). Italian warships did violate Tunisian waters on several occasions before Pedestal and usually the Vichy government either protested or turned a blind eye.

Platon

[Urmel]

I don't think anyone cared very much about Vichy neutrality. I think the DDs that attacked da Giussano and da Barbiano at Cape Bon on 13 Dec 41 also traversed French waters?