Italian submarine Guglielmo Marconi

Leonardo Da Vinci, the most successful Italian submarine in World War II
Class overview
Operators:	Regia Marina  Kriegsmarine  Imperial Japanese Navy
In commission:	1940–1945
Completed:	6
Lost:	6
General characteristics
Type:	Submarine
Displacement:	1,195 long tons (1,214 t) (surfaced) 1,490 long tons (1,510 t) (submerged)
Length:	76.5 m (251 ft 0 in)
Beam:	6.81 m (22 ft 4 in)
Draught:	4.72 m (15 ft 6 in)
Propulsion:	Diesel-electric; 2 × CRDA diesel engines 2 × Marelli electric motors
Speed:	17.8 kn (33.0 km/h; 20.5 mph) (surfaced) 8.2 kn (15.2 km/h; 9.4 mph) (submerged)
Range:	Surfaced: 2,900 nmi (5,400 km; 3,300 mi) at 17 kn (31 km/h; 20 mph); 10,500 nmi (19,400 km; 12,100 mi) at 8 kn (15 km/h; 9.2 mph) Submerged: 8 nmi (15 km; 9.2 mi) at 8 kn (15 km/h; 9.2 mph); 110 nmi (200 km; 130 mi) at 3 kn (5.6 km/h; 3.5 mph)
Test depth:	90 m (300 ft)+
Complement:	57
Armament:	8 × 533 mm (21.0 in) torpedo tubes (4 bow, 4 stern) 1 × 100 mm (4 in) / 47 caliber gun 4 × 13.2 mm (0.52 in) machine guns

The Marconi class was a class of six submarines built for the Royal Italian Navy (Italian: Regia Marina). The submarines were all launched between 1939 and 1940, and all but one, Luigi Torelli, were lost in the Atlantic during the Second World War.

Guglielmo Marconi (pennant number MN) was launched 27 July 1939 and completed on 2 February 1940. On its first wartime patrol in the Mediterranean Sea, Marconi torpedoed the Royal Navy destroyer HMS Escort on 8 July 1940. Marconi sailed on 6 September 1940 and passed the Strait of Gibraltar on 11 September for an Atlantic patrol to Bordeaux on 29 September. En route Marconi sank the neutral Spanish fishing boat Almirante Jose de Carranza. Marconi sank one ship on its first BETASOM patrol from Bordeaux. After an unsuccessful patrol, Marconi sank three ships on its third BETASOM patrol and damaged a Yugoslavian freighter on the following patrol which was later sunk by U-126. Marconi was lost to unknown causes sometime after 28 October 1941 on its fifth BETASOM patrol.

Leonardo da Vinci (pennant number LV) was launched 16 September 1939. da Vinci sailed on 22 September 1940 and passed the Strait of Gibraltar on 27 September for an Atlantic patrol to Bordeaux on 31 October. After unsuccessful patrols from 21 December to 20 January 1941 and from 4 April to 4 May, da Vinci sank one ship on its third BETASOM patrol. After another unsuccessful patrol from 15 August to 24 September, da Vinci sank two ships during Operation Neuland and four ships on the following patrol. After being modified to carry a midget submarine, da Vinci sailed without the midget submarine and sank four ships. Sailing again without the midget submarine, da Vinci sank six ships on its last patrol. While attempting to return to Bordeaux, da Vinci was sunk on 23 May 1943 by the escorts of convoy KMF 15. There were no survivors. Leonardo da Vinci became the top scoring non-German submarine of the entire war.