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Italian Submarine and Convoy Doctrine

jwsleser

Administrator
Staff member
I was asked these two questions about the Regia Marina. Can anyone help answer these?

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The two issues involve Italian submarine doctrine and convoys for an operational game in the Decision at Sea series.

1) It's commonly known that submarine doctrine when Italy entered the war was to assign their subs in the Med to rigid patrol areas, which they were not allowed to leave to pursue targets or for any other tactical reason. When did this doctrine change? English language sources just broadly generalize with verbiage like "by 1942," which isn't especially helpful. And what was the new doctrine?

The Royal Navy finally allowed access to their submarines' WWII logs in the last few years, and the information now available on Uboat.net for those subs is actually better than that for German subs. If similar info was available for Italian subs I could probably answer this question for myself, but it's not available anywhere I can access.

2) Italian convoys were small and usually escorted by only a couple destroyers or torpedo boats, occasionally with distant cover by larger forces. What were their original routes, how often did they sail, and when did they change? They do not seem to have regular designations like the Allies, but one does sometimes see letter designations in sources. How were they designated?

I have a complete list of dates and compositions for the arctic convoys that I did for PQ-17, as well as a complete list of east-west British convoys in the Med (and almost complete for north-south convoys to and from Greece). But all I have for the Italians is anecdotal evidence of the convoys that were attacked by the British, often with no dates/ports of departure or accurate composition. The aforementioned data on Uboat.net for RN Med sub patrols does include some information on the exact composition of Italian convoys the subs attacked which I have never seen elsewhere, clearly from Italian sources. I would like to compile a list of Italian convoys like I have for the Allies, at least as much as possible, so am hoping someone with access to these Italian sources might help with this.
 

DrG

Member
The best I could do would be to refer to the official history of the Italian Navy, but you already know it. I have checked also Aldo Cocchia's "La battaglia dei convogli", but it doesn't provide the information you need.
As far as I have read, most of the convoys, especially since 1941, were identified by the name of one of its merchantmen (I assume it was the leading one).
The routes were planned to keep the ships as far as possible from the aircrafts based in Malta, at least since mid-1941. The Western route, close to Tunisia, was by far preferred because its shallower waters and minefields made submarine attacks more difficult. This is the usual map of Italian routes and Malta-based aircraft ranges: https://en.wikipedia.org/wiki/Siege..._shipping_routes,_Summer_and_Autumn,_1941.jpg
 

jwsleser

Administrator
Staff member
I sent the map from between pages 160-161 in volume VI of the USMM history to the individual. It is basically the same information that is in the Playfair map. I gave him the link to the English translations with a warning that the translation isn't great.

RE: Convoy naming. I came to the same conclusion, i.e. that th convoys were named by a ship in the convoy. There are some exceptions, and I believe they are mainly when major surface units are part of the convoy operation.

How rigid was the rule of using only one torpedo per attack?
 

Dili

Member
I don't think there was restriction for attacks against capital units. But a cruiser would be probably attacked by 2 torpedoes not 4.
Nevertheless notice this limitation most common submarine operating in Med were the 600t. They only had 4 fwd tube and 2 stern. No reloads. Only the Acciaio 600t that appeared in war had 2 reload for fwd.

But there was a change probably in 1942. In Pedestal, Axum fired a spread of 4 torpedoes - all that it had forward and all hit- hit cruiser Nigeria, cruiser Cairo twice(sunk), tanker Ohio.
 
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DrG

Member
According to Cernuschi, "Il sottomarino italiano", p. 41, the launch of all the torpedoes without air bubbles and keeping a constant trim was succesfully tested on the submarine Perla in the summer of 1939 and was introduced in service since the second half of 1940, superseding the previous policy of launching only one torpedo at a time.
 

jwsleser

Administrator
Staff member
The Regia Marina is not my main of research, so I haven't begun to dig deeply into their history beyond convoy work.

Interesting, so the issue was technical and not financial or capacity as implied in English works. I know that there was a limited number of aerial torpedoes and production rates were low. I assume surface and submarine torpedo stocks were adequate.
 

Dili

Member
They were till inadequate quantity. One of the reason at start of war they had sub caliber tube for 450mm.

Most sources(wiki, etc.) continue to incorrectly state 600t had 12 torpedoes.
 
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DrG

Member
The adapters for the launch of the obsolete 450 mm torpedoes were disembarked shortly after the Italian entry into war or kept only for training purposes. The availability of torpedoes was more a concern for the Air Force, which started the war without stocks, but to a lesser extent for the Navy.
 

DrG

Member
Hi Dili. Bagnasco, "Le armi delle navi italiane" confirms your data (by the way, I recall I have read these numbers somewhere, but I don't remember where: may you tell me your source, please?), because he tells that there were about 1.5 torpedoes per tube on the submarines. He does not specify the caliber, anyway, but they were almost all 533 mm, with the notable exception of the four Cagni (Ammiragli) class, which carried 450 mm torpedoes, allowing them to carry a larger amount of torpedoes during their oceanic missions.

The Regia Marina had a stock of 3,650 torpedoes at the beginning of the war, in front of 1,450 torpedo launchers on submarines, MTBs, torpedo boats and destroyers. During the war it launched a total of 3,700 torpedoes, of which 546 in 1940, 1,185 in 1941, 1,600 in 1942 and more than 350 in 1943. Imports were negligible: a few dozens of captured French torpedoes and a few dozens of German G.7e 533 mm electric torpedoes since 1942.

Data about production is hard to find and is always very fragmentary. Moreover, production was made also for the torpedo bombers of the Regia Aeronautica and the Luftwaffe. Anyway, according to Zamagni, "Come perdere la guerra e vincere la pace", towards the end of 1941 the Italian (without distinction between Navy and Air Force) monthly needs of torpedoes amounted to 232 pieces, and the factories of Fiume (Silurificio Whitehead) and Baia - Naples (Silurificio Italiano) planned to meet this requirement by the end of the year. In order to satisfy the German requirements of 320 torpedoes per month by 1942, the factories of Fiume and Baia had to double their production, while that of Livorno (Motofides) to increase it three times.
In May 1938 the monthly production was of 40 torpedoes in Fiume, 10 in Livorno and 40 in Baia.
By November 1941 (the text is unclear; I guess that the correct interpretation is "from the beginning of the year to Nov.") the Silurificio Italiano delivered 397 torpedoes to the Navy, while, on 8 Nov. 1941, the Silurificio Whitehead planned to deliver 650 torpedoes by the end of the year. At the same time, the Motofides delivered 160 torpedoes. Whitehead planned to deliver 1,980 torpedoes to the Navy (of which 270 from the Motofides factory, which was a subsidary of Whitehead) in 1942. In November 1941 the Whitehead had reached a monthly production of 70 torpedoes and the Silurificio Italiano 50 torpedoes.

While these data are of rather difficult interpretation, I have never read of an actual shortage of torpedoes for Italian submarines, i.e. a shortage which really hampered their employement and their doctrine of use during the war. On the contrary, the Regia Aeronautica suffered of a certain lack of torpedoes in several instances, for example against Operation Halberd in Sept. 1941.
 
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DrG

Member
The availability of torpedoes should also take into account the actual number of submarines ready for action, i.e. the ratio between torpedoes and tubes should consider only thse tubes of this latter number of subs and not the total in service.
Bagnasco, "Sommergibili in guerra", p. 189 provides a useful chart of the strength of the Italian submarine force during WW2. I report its data in the following table:
10 June 19401 January 19411 January 19421 January 19438 September 1943
Subs in service11597917777
Subs ready for action9267653745
Subs lost and decommissioned(between the dates)22212626
Subs commissioned(between the dates)4151226
 
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Dili

Member
The 450 tube at start were all for H class, Cagni was not operational yet.
Nevertheless i have 353 modern and 308 old 450mm torpedoes for submarines which leads me to believe that the sub caliber strategy was not due to lack of 533 but a tactic against merchants which also define the Cagni's configuration.

The issue in the Med war was lack of Allied merchants...
 

DrG

Member
Yes, you are right about the Cagni!

I agree that the amount of targets was ideed very limited, and concentrated in heavily escorted convoys. Moreover, the Mediterranean was really a peculiar theater of war for submarines. It mixes areas with shallow waters and other with deep waters, minefields plaid a key role, air cover was almost always possible for the escort of ships, the British used fast merchantmen as much as possible, etc. But I think that the matter of time was the most important one: routes were relatively short, especially if compared to the Atlantic, therefore the time of discovery of an enemy ship (by recon or by sigint) played a crucial role. And, as a consequence, the relative speeds of surface ships and submarines. The 600 class was relatively slow in surface, with a top speed of only 14 knots, while the U-Boot Type VII had a speed in excess of 17 knots. These 3 miles per hour can make a huge difference, especially against fast convoys, both in the probability of reaching the enemy and of concentrating submarines against a single target. The 600 class, instead, had been planned for a saturation of the sea routes between Algeria and France, operating as a kind of armed buoys, therefore neglecting top speed and the number of torpedoes (bases in Sardinia, Sicily or Liguria were very close to the area of operation).

Returning to the consumption of torpedoes, Bagnasco, in his evergreen classic "I sommergibili della Seconda guerra mondiale" (translated in English as "Submarines of World War Two"), reports that Italian submarines in the Mediterranean launched a total of 427 torpedoes during the war. No data are provided for the submarines active in the Atlantic and Indian oceans.
 
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