May 1943
| 7 | May | Allied forces entered Tunis. |
| 7/8 | May | Operation B.G.6 (attack on Gibraltar shipping by human torpedoes from Olterra). |
| 13 | May | The last Axis forces surrendered in Tunisia. The whole North African coast was now in the hands of the United Nations. |
| 24 | May | U-boats were defeated in the Battle of the Atlantic. Dönitz was forced to withdraw them temporarily. From now on, they would be on the defensive. |
Italian submarine patrols in the Mediterranean during May 1943
| Dandolo (…4 May) | Topazio (…4 May) | Aradam (2-16 May) |
| Diaspro (2-17 May) | Zoea (4-8 May) Pt.1 | H.8 (5-6 May) |
| H.2 (5-6 May) | Ametista (6-27 May) | Onice (6-27 May) |
| Zoea (8-12 May) Pt.2 | H.6 (10-11 May) | H.6 (12-13 May) |
| H.2 (12-13 May) | Bragadino (12-16 May) Pt.1 | H.6 (14-15 May) |
| Gorgo (14 May…) | Nichelio (15 May…) | Bragadino (17-24 May) Pt.2 |
| Atropo (23-30 May) Pt.1 | H.2 (24-25 May) | H.8 (24-25 May) |
| H.2 (25-26 May) | H.8 (25-26 May) | Beilul (26 May…) |
| Platino (29 May…) | Brin (29 May…) | Atropo (31 May…) Pt.2 |
| Alagi (31 May…) |
Due to the increasing threat of enemy air raids, VII Grupsom was forced to relocate from Cagliari to La Maddalena. Delayed by defects, Argento was the last submarine to leave and made the trip on one engine (16-18 May). Similarly, X Grupsom in Augusta had ceased to be an offensive flotilla in March 1943; the base was used by transport submarines until the beginning of June.
On 5 May, while being transferred from La Maddalena to Naples for refit, Dandolo (T.V. Aldo Turcio) sighted a periscope and fired a single torpedo. After about four minutes, two explosions were heard in quick succession, and it was believed that the enemy had fired back a torpedo, and both exploded at the end of their run. The sighting appears to have been bogus.
Loss of FR.116 (ex-Turquoise) and FR.117 (ex-Circé)
FR.116 (ex-French Turquoise) and FR.117 (ex-French Circé) were scuttled on 6 May in Bizerte as they could not sail to safety, and within a few days, the Allies took the last foothold on the North African coast.
Onice (C.C. Ferdinando Boggetti) had sailed from Leros for a patrol off Benghazi when, at dusk, she sighted three bombers and immediately dived. These were three Baltimore from 454 Squadron (RAAF) returning from an anti-shipping strike in the Aegean. The bomber (AH158) piloted Flight Lieutenant Moore was the only one to react in time and released two 250-lb bombs; they caused no damage. Another bomber (AG869) piloted by Sergeant D. Todhunter only managed a short burst of machine gun fire from long range.
Operation B.G.6
During the night of 7/8 May, three human torpedoes were launched from the Olterra to Gibraltar to attack shipping with limpets. They were respectively manned by C.C. Ernesto Notari/2o Capo Palombaro Ario Lazzari, Ten. G.M. Camillo Tadini/S.C. Pal. Salvatore Mattera and S.T.V. Vittorio Cella/S.C. Pal. Eusebio Montalenti. The attackers took advantage of a storm and were successful. At dawn, the American Liberty ship Pat Harrison (7,191 GRT, built 1943) [one killed and one badly wounded] and the British Mahsud (7,540 GRT, built 1943) [one missing] and Camerata (4,875 GRT, built 1931) [two killed] were damaged by explosions.
During the night of 12/13 May, Diaspro (T.V. Alberto Donato), on patrol east of the Balearic Islands, was forced to dive to a depth of 50 metres by an unidentified aircraft. No attack developed. However, Donato was informed of a leak through the No.6 torpedo tube. The submarine surfaced, and at dawn, a rating who had donned a diving apparatus managed to remove an obstruction from the tube door, and the leak was stopped. On 17 May, the submarine was returning to La Maddalena when she came under fire from a coastal battery at Porto Torres (Sardinia), but firing was checked after recognition signals were made and the Italian flag properly displayed.
Loss of Mocenigo
At about 1415 hours on 13 May, bombers of the USAAF raided Cagliari harbour. The submarine Mocenigo (T.V. Alberto Longhi), undergoing repairs, was near-missed several times and finally sank. There were only ten crew members on board at the time and they were all evacuated safely.
Loss of Gorgo
At 2200 hours on 14 May, Gorgo (C.C. Innocenzo Ragusa) sailed from Cagliari for a patrol east of the Balearic Islands but disappeared without a trace. On 21 May, French Latecoère 298 seaplanes on anti-submarine patrol off Oran detected an oil patch moving to the northwest at 2-3 knots. They attracted the attention of the destroyer USS Nields (DD-616). At 1818 hours, she attacked a contact with a pattern of nine depth charges and another depth charge pattern six minutes later, and some debris was seen. This attack has been attributed to the destruction of the Italian submarine, but this is doubtful as it was not in her patrol area. No other valid claim appears to have been filed, which could explain the disappearance of this submarine. It is possible that she hit a drifting mine, or her loss was accidental.
At 2225 hours on 17 May, in 40°23’ N, 07°48’ E, Argento (T.V. Leo Masina) came under attack by Hudson ‘P’ of 608 Squadron (Squadron Leader P. Meston), which dropped three 100-lb bombs on a first run and three depth charges on a second one. The submarine replied with her anti-aircraft weapons and dived to safety just before the second run.
Shortly after midnight, on 22 May, Bragadino (C.C. Francesco Pedrotti) was on passage from Augusta to Taranto when, off Cape Murro di Porco, she spotted four torpedo tracks and took evading action just in time. They were fired by HMS Unruly (Lt J.P. Fyfe, RN) from a range of 3,000 yards.
Beilul (T.V. Pasquale Beltrame), having sailed from Leros for a patrol in the Gulf of Sirte, was some seventy-five miles north of Derna when, on the morning of 28 May, she was surprised by two Beaufighters (mistaken for Blenheims) from 227 Long Range Fighter Squadron (201 Group) piloted by Flight Lt M.B. Curtis and Flight Officer M.B.E. Amos. Fortunately, they had already expended their bombs on a caique and could only attack with cannon fire. The Italian gunners put up an accurate anti-aircraft defence, and the submarine dived at the first opportunity.
During a visit to Italy, Grand Admiral Dönitz expressed the desire to obtain the submarines Brin (Aquila X) and Dandolo (Aquila XI) to be used as transports for the Far East. The Italians were interested in an exchange with two type IXC submarines. Dönitz thought that type VIIC would be more appropriate for their needs. A third submarine (Mocenigo), which was also deemed suitable, had just been destroyed in Cagliari harbour. With the threat of an Allied invasion imminent and every submarine needed to repel it, on 23 April, Supermarina put forth the condition that the German-built submarines would have to reach Italy before the exchange could occur. The submarine offered by the Germans was the type VIIC U-1162 (to be renamed S.10) but does not appear to have been taken over by the Italian Navy before the Armistice.
Italian submarine patrols in the Atlantic and Indian Ocean during May 1943
| Da Vinci (…23 May*) | Cappellini (11 May…) | Tazzoli (16-24?May*) |
| Giuliani (23 May…) |
During the night of 9/10 May, the RAF laid sixty-two mines in the Gironde and off La Pallice.
Early in the afternoon of 17 May, Bordeaux was heavily bombed. There were a few casualties among the Regia Marina personnel. The submarines Cagni, Bagnolini, Finzi, Torelli, and Barbarigo were present but escaped direct hits.
Gamma men attempt at Huelva
On the night of 12/13 May, the gamma swimmers Sottocapo Salvatore Nizzi and 2o Capo Carlo Vianello of Group G.O.G. [based on the Italian merchant ship Gaeta anchored at Huelva] claimed to have planted limpets on the hull of a 9,700-ton steamer identified as Ladovich. British sources did not confirm this, nor did the existence of such a ship.
Loss of Enrico Tazzoli
On 16 May, Tazzoli (C.C. Giuseppe Caito) departed from Bordeaux for Singapore with 165 tons of stores. She was believed lost between 17 and 24 May, possibly mined when she left Bordeaux. Six officers, forty-six ratings, and five civilians were missing. The destroyer USS Mackenzie attacked a submarine on 16 May, in position 38°53’ N, 20°33’ W, and another on 22 May. It is impossible that Tazzoli was lost in the first attack, as it probably accounted for U-182 (KL Nicolai Clausen), but the second was a possibility. Also, on 16 May, in position 45°57′ N, 11°40′ W, Halifax ‘R’ (HR774) of 58 Squadron piloted by Pilot Officer A.J.W. Birch) attacked a submarine with depth charges, and some sources have attributed the loss of Tazzoli to this attack, but she could not have travelled fast enough to reach that position in time. This attack sank U-463 (KK Leo Wolfbauer). However, on 20 May, Liberator ‘A’ from 224 Squadron, piloted by Flying Officer J.R. Weeds, attacked a surfaced submarine proceeding on course 270° at 8 knots in 45°50’ N, 09°27’ W. Six depth charges were released, but no conclusive results were observed. This could have been Tazzoli, but we will never know for sure.
Loss of Leonardo da Vinci
On 23 May, the destroyer HMS Active (Lt Cdr P.G. Merriman, RN) was screening convoy KMF.15, some 290 miles west by south of Cape Finisterre. At 1130 hours GMT, as the vessels were coming out of a rain squall, a submarine’s conning tower and periscope were sighted at 6,000 yards. Asdic contact was obtained and a first pattern of ten depth charges was dropped by the destroyer. Shortly after, she was joined by the frigate HMS Ness (Cdr. T.G.P. Crick, DSC, RN), and the two vessels alternated with the release of depth charges when an underwater explosion was heard. As Active was ordered to resume the escort of the convoy, Ness lingered in the area, and the sinking was apparently confirmed by the recovery of wood, cork, and coffee tins marked with ‘Napoli’ and a pair of human lungs.
There is little doubt that Da Vinci (C.C. Gianfranco Gazzana Priaroggia) was sunk in this attack. There were no survivors; nine officers and fifty-four ratings perished.
Thus, the two most famous Italian submarines disappeared within days of each other. The blow was not limited to Italian submarines; in the same month, some forty German U-boats were sunk. It was a turning point in the Battle of the Atlantic. Admiral Dönitz ordered the withdrawal of his submarines from the North Atlantic until a solution was found to counter Allied measures.