With coastline as long as that of Italy's, it behooved the nation to promote considerable naval firepower across the Mediterranean with all of its critical waterways and trading routes. While the Italian surface fleet of World War 2 was well-represented through various battleships and other impressive surface vessels, its submarine fleet made up the important undersea component. One of its submarines became Ammiraglio Cagni which served throughout the war in Italian hands, though she would eventually switch loyalties as the nation ultimately ended its support of Germany and its Axis-aligned powers by the end of 1943.
Ammiraglio Cagni served as the lead ship of the Ammiraglio Cagni-class of attack submarines - properly classified as ocean-going commerce raiders charged with targeting enemy shipping - for the Italian Navy (Regia Marina). Her primary service years were during World War 2 (1939-1945) in which she conducted twenty-three sorties and managed to sink several vessels before the Italian government signed the armistice with the Allies. Cagni was launched on July 20th, 1940 and her sisters would go one to include Caracciolo, Millo and Saint-Bon - none of which survive today (2014) as they were either scuttled or sunk in action.
Ammiraglio Cagni was named after Umberto Cagni, an admiral once having served with the Royal Italian Navy and largely known for his exploration of Arctic in attempting to reach the North Pole at the turn of the last century. He served during World War 1 (1914-1918) and ultimately retired from service in 1923, having attained the rank of admiral.
As built, Cagni displaced 1,650 tons when surfaced and 2,140 tons when submerged. She featured a running length of 88 meters with a beam reaching 7.8 meters and draught of 5.7 meters. Propulsion was by way of a diesel-electric combination system driving twin shafts at 4,370 horsepower and 1,800 horsepower respectively. Diesel power was used when the vessel was surfaced - the primary form of travel - while the electric system drove the boat when submerged, albeit at a slower pace and for a shorter duration. As with all "hybrid" submarines of the period, Cagni was required to surface to recharge her batteries, expel dangerous CO2 gasses and take on new oxygen stores for the crew. This provided her most vulnerable period during active operations. The boat could make headway at 17 knots when surfaced and up to 9 knots when submerged. Her entire crew complement numbered 85 and included officers and enlisted.
Armament was settled around an impressive 14 x 450mm torpedo tubes arranged as eight bow-facing and six rear-facing. However, these were decidedly smaller in caliber than the widely-accepted 533mm types used in other attack submarines of the period - reason being that the Italian Navy though 450mm torpedoes proved sufficient in engaging lesser foes such as merchant vessels. The Cagni was also outfitted with 2 x 100mm deck guns for surface attack and 4 x 13.2mm heavy machine guns as an aircraft deterrent. The Cagni was afforded 36 total torpedo reloads.
Cagni began operational service undertaking various patrols throughout the Mediterranean Sea. Her career in the region saw her sink two enemy ships - Dagomba, a British tanker vessel, and Argo, a Grecian sloop. Both were targeted and sunk on November 29th, 1942. Her tour of the Mediterranean saw her complete some twenty-one total missions (five of the transport variety) before being relocated for service in the South Atlantic into 1943. Once there, she undertook just two missions before receiving word that the government has surrendered. In turn, Cagni was handed over to the Allies (Britain) on September 20th at Durban, South Africa.
After her service as an Axis submarine, Cagni began operations as part of the Allied contingent. She served in a training role form January 1944 onwards and would survive to the end of the war in Europe in May of 1945. Eventually decommissioned from active service in 1948, the boat was given up and scrapped ending her formal ocean-going career.