Italian submarine Acciaio

The Italian submarine Acciaio was the name ship of her class of submarines built for the Royal Italian Navy (Regia Marina) during World War II.

Design and description
The Acciaio-class submarines were designed as improved versions of the preceding Adua-class submarine. They displaced 697 t surfaced and 850 t submerged. The submarines were 60.18 m long, had a beam of 6.44 m and a draft of 4.78 m.

For surface running, the boats were powered by two 700 bhp diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 400 hp electric motor. They could reach 14 kn on the surface and 7.3 kn underwater. On the surface, the Acciaio class had a range of 5000 nmi at 8.5 kn, submerged, they had a range of 80 nmi at 3 kn.

The boats were armed with six internal 53.3 cm torpedo tubes, four in the bow and two in the stern. They were also armed with one 100 mm deck gun for combat on the surface. The light anti-aircraft armament varied and could consist of one or two 20 mm or one or two pairs of 13.2 mm machine guns.

Construction and career
Acciaio was built in OTO's shipyard at Muggiano. She was laid down on 21 November 1940 and launched on 22 January 1941. She was commissioned on 30 October of the same year. The name Acciaio means "Steel" in Italian. The boat’s first patrol was on 29 March 1942 and she carried out nine offensive patrols during her service career, against Allied naval forces in the Mediterranean. She had one success, when she sank the British armed trawler HMT Tervani on 7 February 1943 off the Algerian coast. Her last patrol was on 10 July from La Maddalena to act against Allied forces involved in Operation Husky, the invasion of Sicily. On 13 July 1943, Acciaio was sunk by the British submarine HMS Unruly (P49) with the loss of her entire crew of 46.