In a previous post (at this link) I had written about the use of German sonar (S-Geraet) and depth charges by the Italian navy, the Regia Marina. This commenced at the end of 1941, and gave the Regia Marina an important new capability in providing convoy defense on the North Africa route, which led to some quick successes, such as the sinking of HMS P-38 (see also this link). A technical description of the history and functioning of the S-Geraet can be found at this link.
In the post below, I have translated a report of the Special Command of the German navy, the Kriegsmarine, which was charged with the task of overseeing the operation of the German equipment on the Italian vessels. The document is from the war diary of the German Liaison Staff at the Admiralty of the Royal Italian Navy, and can be found in NARA under T-1022 Roll 2481.
Overview of the Activity Carried Out Thus Far by the Special Command for the Installation and Deployment of German S-Geraete on Units of the Royal Italian Navy
(Commenced 17 November 1941)
1.) Introduction followed proposals made by Chief Naval Liaison Command to Italian Navy during July 1941.
1 Officer (Commander Ahrens)
1 Chief Petty Officer
3 Non-Commissioned Officers from the Submarine Defense School Gotenhafen
Furthermore listening crew (from destroyer Lody, strength 1/4 from beginning November to mid-December on Torpedo Boat (Torpediniera) Castore, and listening crew strength 1/4 on destroyer Da Mosto from beginning November to 1 December. 3 other ranks were killed when the boat was sunk. The NCO and one man remain at the disposal of the Special Command.
At the start of the activity:
Clearance of specific questions of detail concerning submarine defense with the relevant Italian offices, especially Admirals Strazzari and Da Zara. Determination of equipping Italian vessels with S-Geraet installed with German depth charges and depth charge throwers.
Instruction of Italian crew and shore personnel in various naval stations about installation and maintenance of the German depth charges.
Schooling of listening and depth charge crews on the units with S-Geraet installed. Carried out trials.
Instruction of all captains in all questions relating to submarine defense, especially about the method of attack. Participation in combat missions.
c) Successes of Italian vessels equipped with S-Geraet up to 28 February 1942.
1.) Torpedo boat Castore near Gaeta on 24 November 1941: based on S-Geraet location report evaded two torpedo trails. Carried out attack with 36 depth charges. Destruction of submarine possible. German listening crew.
2.) Destroyer Da Mosto, southern tip of Sicily, 27 November 1941: location of an unknown minefield. German listening crew.
3.) Torpedo boat Lince, Gulf of Taranto, early December, attack on located submarine with Italian depth charges. Success questionable. Italian listening crew and Construction Advisor Morgenstern.
4.) Torpedo Boat Orsa, 115 Degrees, 63 nautical miles off Sfax on 7 January 1942. Attack on located submarine with 30 German depth charges. Success: initially strong aural location ceases; location continues to show in large oil slick. Location of attack had to be left early to ensure protection of the escorted steamer. Italian and German listening crew, directed by Commander Ahrens.
5.) Torpedo boat Sagittario at Cape Ducato on 8 February 1942. Evaded torpedo. Enemy submarine rammed, has to be considered destroyed. Torpedo boat heavy damage on the bow. German and Italian listening crew.
6.) Torpedo boat Circe on 13 February 1942: located enemy submarine was fixed for six hours. Submarine surfaces after 3 attacks with German depth charges; 23 prisoners made. Attempt to bring her in fails, boat sinks. English submarine “Tempest”. German and Italian listening crew.
7.) Torpedo boat Pallade at Capo dell’Armi on 16 November 1942. Located submarine attacked in three runs with 45 German depth charges. At water depth of 1,600m signal ceases after final attack. Oil slick of 1,000 x 2,000 m. German and Italian listening crew, directed by Commander Ahrens.
8.) Torpedo boat Circe at Ras Hallab on 23 February 1942. During escort of convoy attacking submarine is located and periscope is sighted. 10 depth charges dropped on diving location. Submarine surfaces briefly, twice, and finally sinks. Bag with flags, parts of interior (door of cupboard, tabletop), cans of biscuits and cigarettes as well as human body parts come up. Large oil slick. Continuous rising of air bubbles. German and Italian listening crew.
d) Intended equipping of Italian naval and merchant units
1.) 29 S-Geraete of which one fixed in Spezia. One further S-Geraet lost when destroyer da Mosto was sunk.
2.) 40 depth charge throwers, 72 reloading installations, 20 depth charge rails, 60 single depth charge holders.
3.) 4,000 depth charges Type Dora
2,000 depth charges Type Fritz
1,500 stamps and cartridges for depth charges WB D60m and WB F40m.
By 28 February 1942, 10 Italian torpedo boats and 1 destroyer as well as 9 auxiliary vessels have been equipped with the S-Geraet.
For equipping further Italian naval units with S-Geraet, see attached list, Appendix 17.
R.N. Pallade, a Spica-class, Alcione sub-class Torpedo Boat, photographed pre-war. Courtesy of Wikipedia.
 Ubootabwehrschule (UAS)
1 NCO, 4 other ranks
 There is no submarine loss recorded for this day, and no attack in the region of Gaeta either. I used the ASA database at this link for checks.
 Baurat, a German civil servant grade. I have not verified this attack.
 This was not actually a successful attack – see this link, in particular comments below.
 The submarine was HM/Sub Proteus (N29), and while she was damaged, it appears she came off better than Sagittario. Details from the crew of HM/Sub Proteus can be found at this link.
 This will follow in another post.