High Quality Content by WIKIPEDIA articles! 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 German submarine base (BETASOM) at Bordeaux in August 1940. After four boats had been sunk in the Atlantic, Barbarigo and Comandante Cappellini (sometimes also called 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. Only Dandolo was in operational condition at the end of the war.