The Cagni- or Ammiraglio Cagni-class was a class

Ship class

A ship class is a group of ships of a similar design. This is distinct from a ship-type, which might reflect a similarity of tonnage or intended use. For example, the is a nuclear aircraft carrier of the Nimitz class....

 of submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s built for Italy's Regia Marina

Regia Marina

The Regia Marina dates from the proclamation of the Kingdom of Italy in 1861 after Italian unification...

 during World War II.

Design

These submarines were designed as commerce raiders for oceanic operations. They had high endurance and a large torpedo load for extended patrols. A smaller 450 mm torpedo was chosen, rather than the standard 533 mm, as the Italians believed this was adequate to deal with merchant ships. The boats were designed to have the range to sail non-stop from Italy to Kismayu

Kismayu

Kismayo or Kismayu is a port city in the Jubbada Hoose province of Somalia. It is the commercial capital of the autonomous Jubaland region....

, Italian Somaliland

Italian Somaliland

Italian Somaliland , also known as Italian Somalia, was a colony of the Kingdom of Italy from the 1880s until 1936 in the region of modern-day Somalia. Ruled in the 19th century by the Somali Sultanate of Hobyo and the Majeerteen Sultanate, the territory was later acquired by Italy through various...

 where a new submarine base was to be built. In order to operate in the Indian Ocean

Indian Ocean

The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 Monsoon

Monsoon

Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...

 the submarines were fitted with large conning towers and armed with two 100 mm guns.

The large conning towers were rebuilt to a smaller German style as a result of war experience. The Ammiraglio Cagni carried out a 4.5 month patrol in the South Atlantic during 1942-43. The other three boats were used as transport submarines to supply Italian forces in North Africa.

Ships

All four boats were built by CRDA Monfalcone, laid down in 1939 and completed in 1941

Ship	Namesake	Launched	Service / Fate
Ammiraglio Cagni	Umberto Cagni Umberto Cagni Umberto Cagni was a polar explorer and an admiral in the Royal Italian Navy. He is best known for his leadership in a probe, by dogsled, northward over the surface of the Arctic Ocean in 1900...	20 July 1940	Surrendered to the japanese in Colombo in september 1943, renamed as I-507, broken up in 1948
Ammiraglio Caracciolo	Francesco Caracciolo Francesco Caracciolo Prince Francesco Caracciolo was a Neapolitan admiral and revolutionist.-Early life and British service:Caracciolo was born in Naples to a noble family. He entered the navy and learned his seamanship under Rodney...	16 October 1940	Scuttled after damage by HMS Ferndale, near Bardia, 11 December 1941
Ammiraglio Millo	Enrico Millo Enrico Millo Enrico Millo was an Italian admiral and politician. As a military commander, he led the raid against the Turkish navy in the Dardanelles.- Life :...	31 August 1940	Sunk by British submarine HMS Ultimatum, 14 March 1942
Ammiraglio Saint-Bon	Simone Antonio Pacoret de Saint Bon	6 June 1940	Sunk by British submarine HMS Upholder HMS Upholder (P37) HMS Upholder was a Royal Navy U-class submarine built by Vickers-Armstrong at Barrow-in-Furness. She was laid down on 30 October 1939, launched on 8 July 1940 by Mrs. Doris Thompson, wife of a director of the builders. The submarine was commissioned on 31 October 1940... , 5 January 1942

12 more boats were planned for the 1940 and 1941 ship building programmes but were cancelled as a result of the outbreak of World War II

Ammiraglio Cagni

Her first operational patrol were in the Mediterranean, doing 5 missions of transport and 16 of patrol. Her first mission in the atlantic was of 136 days, sinking to the british tanker Dagomba and the greek sloop Argo.

In her second mission, she sailed to the Indic Ocean for attack allied convoys. However, in that moment Italy surrendered and Cagni surrendered to the Japanese Navy in Colombo. Completly to the IJN service, she was renamed as I-507 and used as school ship, because to her low speed impeded serve for another function. Mussolini tried to recover to the Cagni in 1944, but the japanese refused this.

In 1945 july, she was attacked and sunk by 2 B-25 bombers in the shallow waters of the Gōtō Islands. The hull was raised by the U.S in november 1945 (2 months after of the japanese surrender) and scrapped in 1948.

Ammiraglio Caracciolo

In december 11, 1941, she unsuccessful attacked a british convoy and suffered damage by the depth charges and gunfire of the destroyer HMS Ferndale. Then, she was scuttled for avoid to be captured. 53 men were rescued -and done prisoners- by the british destroyer.

Ammiraglio Millo

She done only 8 missions and this 8 missions was of transport. In march 14, 1942, after of return in a patrol in the waters of Malta, she was torpedoed and sunk by the submarine HMS Ultimatum, with the loss of 57 members of her crew.

Ammiraglio Saint-Bon

She done only 10 missions (of transport). She was sunk by the submarine HMS Upholder in January 5, 1942; only 3 crewman survived.