The Regio submarine AMBRA was built at the shipyards Odero Terni between 1935 and 1936. It was one of the ten PERLA Class submarines. She was one of her class attached to the Decima MAS Flotilla. She was the last to be transformed into a carrier of the Maiali (two man torpedoes) and it was also the only one not sunk in that mission.

Displacement: 696/700 tons
Length: 60.18 meters
Beam: 6.45 meters
Draft: 4.60 meters
Power: (diesel) 1,400 hp
Power: (electric) 800 hp
Speed: (diesel) 14 knots
Speed: (electric) 7.5 knots
Bunkers: unknown
Range: (diesel) 5,200 miles @ 8 knots
Range: (electric) 75 miles @ 4 knots
tubes: (fwd) four tubes (21 inch)
tubes: (aft) two tubes (21 inch)
tubes: carried 12 torpedoes
Deck guns: single 100mm .47 cal.
AA guns: four 13.2mm
Crew: 45 men
Depth of dive: 80 meters

In June 1940, AMBRA was attached to the IV Group Submarines, 47th Squadron based at Taranto. Shortly thereafter, she was transferred to the new base as Augusta on Sicily and attached to the X Group Submarines.

AMBRA and U-331 Dockside

In the first phase of the war, the units of X Group had to oppose the Allied convoys bound for Malta. On the night of 31 March 1941 under C.C. Mario Arillo, AMBRA intercepts a British convoy south of Crete. The surfaced submarine has contact with an escort and torpedoes, and sinks, the 5,450 Royal Navy light cruiser HMS BONAVENTURE 90 miles south of Crete.

The Royal Navy destroyer HMS STUART attacks and AMBRA dives. Even with severe damage from the depth charges, she returns to her homeport at Augusta 4 April 1941.

After finishing her repairs in the dockyard summer of 1941, AMBRA is attached to the Decima MAS Flotilla. In October of 1941, AMBRA enters the shipyards at La Spezia for major refit with modifications to her tower, rapid diving system, silent motors and had hangars added to accommodate three Maiali units.

There was one watertight hangar installed on the foredeck and two on the afterdeck for the Maiali units.

In spring of 1942, AMBRA underwent sea trials to test the new systems that were installed, operating in the Gulf of La Spezia.

2 April 1942, AMBRA went to La Spezia to organize a ceremony to honor submarine commanders and crews of the Mediterranean Axis Fleet. Honors were accorded to:

GUGGENBERGER (269-+-1987) Skipper of U-81 who sank the 22,600 ton Royal Navy aircraft carrier HMS ARK ROYAL;

Von TIESENHAUSEN (268-+-1987) Skipper of U-331 who sank the 31,100 ton RN battleship HMS BARHAM – the ONLY battleship sunk on the high seas by submarine of the U-Bootwaffe;

Prince Borghese, Skipper of the Italian submarine SCIRÉ that had sent his Maiali into Alexandria Harbor to sink the 32,700 ton RN battleships HMS VALIANT and HMS QUEEN ELIZABETH.

Apparently SCIRÉ was in the yards, so AMBRA took her place.

After the ceremonies, AMBRA was ready for her first mission with the Decima MAS Flotilla. She was repainted with an unusual camouflage of white tower, above the waterline was grey clear and below the waterline, she was dark grey. She departed La Spezia a few days after the ceremony.

Ambra with hangers on deck

Her mission (B.G.4) ordered AMBRA to a raid on the British base at Alexandria. She followed a rout similar to that of SCIRÉ in her successful mission of December 1941, but with different results. On 14 May 1942, the mission is a failure and AMBRA returns to her homeport at La Spezia.

In summer of 1942, with the loss of SCIRÉ off the harbor at Haifa, the Decima MAS Flotilla has only AMBRA in operation.

In the winter of 1942, the HQ of Regia Marina orders a new mission for the men of Decima MAS flotilla and AMBRA. Order (N.A.1) sends them to attack Algiers Harbor. This mission is set to coincide with the dark of the new moon in December 1942. At the same time, a mission was ordered against the British base at Gibraltar. This mission under order (B.G.5) was given to the Decima frogmen who were hidden in the Italian ship OLTERRA.

EDITOR NOTE – we reported on OLTERRA some issues back. She was in a Spanish harbor near Gibraltar and with major modifications, had an open bay in the hold so that frogmen could swim in and out undetected. They were quite near to Gibraltar.

British spies alert the Royal Navy of the departure of AMBRA on her special mission, and this also puts the mission at Gibraltar in jeopardy. They believe that AMBRA is headed for Gibraltar, and so the Royal Navy increases defenses. In the night of 7 December, the three Maiali units from OLTERRA are spotted by the British and attacked. Two units are sunk, three men are dead.

Next day, the British HQ will announce that AMBRA is sunk.

However, AMBRA reached the harbor at Algiers with her three Maiali units and ten frogmen (Swimmers Gamma). In the night of 11 December, they attack and they are not detected. Explosive charges are attached to five ships anchored in this African harbor.

The 1,493 ton Norwegian steamer BERTO is sunk while the 7,041 ton British EMPIRE CENTAUR, the 7,174 ton British OCEAN VANQUISHER and the 4,558 ton British ARMATTAN are severely damaged.

The attack on Algiers Harbor was the last operation performed by the Decima MAS Flotilla with the use of a submarine. Later the Decima’s men again attacked Gibraltar (orders B.G.6 and B.G.7) from their secret base in the old steamer OLTERRA and the Alessandretta/Mersina (Syria) harbor (Operation Star) with a Swimmer Gamma, hitting nine Allied ships of about 60,000 tons.

Back at the La Spezia shipyards, men of the Decima MAS Flotilla worked feverishly on the new FLUTTO Class submarine and new micro-submarines CA 3 and CA 4. They were preparing a new mission for AMBRA, probably with the mini-submarine CA-3 but on 8 September 1943, Italy surrendered.

On 9 September 1943, AMBRA was scuttled by her own crew but in January of 1944, she is salved and recommissioned by the new Italian Social Republic Navy. She is repaired and refitted, and returned to her former base at La Spezia where Allied bombers sank her in summer of 1944. In 1946, the wreckage of AMBRA was pulled from the harbor and broken up.