Marcello-class submarine

German submarine UIT24 in the Inland Sea, Japan, August, 1944. UIT-24 was the ex-Italian submarine Comandante Cappelini and was later the IJN I-503.
Class overview
Operators	Regia Marina  Kriegsmarine  Imperial Japanese Navy
In commission	1938–1947
Completed	11
Lost	10
Scrapped	1
General characteristics
Type	Submarine
Displacement	1,060 long tons (1,077 t) surfaced 1,313 long tons (1,334 t) submerged
Length	73 m (239 ft 6 in)
Beam	7.19 m (23 ft 7 in)
Draught	5.1 m (16 ft 9 in)
Propulsion	Diesel-electric 2 × CRDA diesels (first 9 vessels) 2 × Fiat diesel engines (last 2 vessels) 2 × CRDA electric engines (all vessels)
Speed	17.4 knots (20.0 mph; 32.2 km/h) surfaced 8 knots (9.2 mph; 15 km/h) submerged
Range	2,500 nmi (4,600 km) at 17 knots (31 km/h) surfaced 7,500 nmi (13,900 km) at 9.4 knots (17 km/h) surfaced 8 nmi (15 km) at 8 knots (15 km/h) submerged 120 nmi (220 km) at 3 knots (6 km/h) submerged
Test depth	100 m (330 ft)
Complement	58
Armament	8 × 533 mm (21 in) torpedo tubes (4 bow, 4 stern) 2 × 100 mm (4 in) / 47 caliber guns 4 × 13.2 mm (0.52 in) machine guns

The Marcello class was a class of nine submarines built in 1937 and 1938 by CRDA in Trieste for the Royal Italian Navy (Italian: Regia Marina). Two similar submarines built in 1939 at La Spezia by Oto Melara are sometimes considered part of the class. All eleven served in the Mediterranean Sea at the start of the Second World War. After Provana's 1940 sinking, the remaining boats were transferred to the BETASOM Atlantic submarine base at Bordeaux in August 1940. After four boats had been sunk in the Atlantic, Barbarigo and Comandante Cappellini were then selected for conversion to "transport submarines" in order to exchange rare or irreplaceable trade goods with Japan. Cargo capacity of 160 tons reduced reserve buoyancy from 20–25% to 3.5–6%; and armament was reduced to defensive machine guns.^[1] Only Dandolo was in operational condition at the end of the war.