The Argo-class submarines displaced surfaced and submerged. The submarines were long, had a beam of and a draft of. Their crew numbered 46 officers and enlisted men. For surface running, the boats were powered by two diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the Argo class had a range of at ; submerged, they had a range of at. The boats were armed with six internal torpedo tubes, four in the bow and two in the stern for which they carried a total of 10 torpedoes. They were also armed with a single Škoda 10 cm K10#OTO 100.2F47 History| deck gun, forward of the conning tower, for combat on the surface. The light anti-aircraft armament consisted of four single Breda Model 1931 Machine Gun| machine guns.
Ships
''Argo''
Argo was launched 24 November 1936 and completed on 31 August 1937. Argo completed two unsuccessful wartime patrols in the Mediterranean before passing the Strait of Gibraltar on 8 October 1940 for an Atlantic patrol to Bordeaux on 24 October. During its first BETASOM patrol, Argo damaged convoy HG 47 escort on 1 December and sank a freighter from convoy OB 252 on 5 December 1940. First Lieutenant Alessandro De Angelis was lost overboard and drowned in heavy seas as Argo was returning to port. The second and third BETASOM patrols from 27 February to 28 March and from 19 May to 12 June 1941 were unsuccessful. Argo left France on 11 October, passed the Strait of Gibraltar on 20 October, and reached Cagliari on 24 October 1941. After refit, Argo patrolled off Cape Ferrat from 6 to 21 April and off Cap Caxime from 22 to 29 May 1942, where it sustained damage from aerial attacks requiring another period of repairs. After patrolling off the Balearic Islands from the 15 to 26 October and off the island of Galite from the 29 to 30 October, Argo entered the Bay of Bougie on 11 November 1942 to torpedo the anti-aircraft ship and the troopship, which had been damaged by aerial bombing during Operation Torch. Argo then patrolled off the north African coast from 17 December to 8 January 1943, and during February, April and June. After two patrols off Sicily in July, Argo was refitting at Monfalcone until the armistice of September 8, 1943. Argo was scuttled when German troops captured the shipyard on 10 September. The Germans salvaged her, but scuttled her at Monfalcone, Friuli-Venezia Giulia, Italy, on 1 May 1945.
''Velella''
Velella was launched 18 December 1936 and completed on 1 September 1937. Velella was on patrol in the eastern Mediterranean when Italy declared war. After refit at La Spezia, Velella sailed on 25 November 1940 and passed the Strait of Gibraltar on 1 December for an Atlantic patrol to Bordeaux on 25 December. After four unsuccessful Atlantic patrols, Valella returned to the Mediterranean on 24 August 1941. After refit at Cagliari and training at Pula, Velella patrolled without success south of Cape Palos in April 1942, south of the Balearic Islands in June, along the Tunisian coast in July, and west of the Island of Galite in August, south of the Balearic Islands in September, in the Gulf of Philippeville and the Bay of Bona in November, north of Cape de Fer in April 1943, and off eastern Sicily in July. Its last patrol was off Salerno, where it was torpedoed by on 7 September 1943. There were no survivors.
