Gisueppe Finzi began conversion into a transport submarine in 1943, but was captured by the Germans in September 1943 before it was completed and redesignated as UIT-21.

[1] Giuseppe Finzi (pennant number FZ) was laid down by Odero-Terni-Orlando (OTO) at their Muggiano, La Spezia shipyard in 1932, launched on 29 June 1935 and completed the following year.

The third patrol near the British Isles from 24 October to 4 December 1940 revealed that the diesel engine air intake was too exposed for North Atlantic winter weather.

During the sixth patrol from 7 to 29 December 1941 Pietro Calvi, Giuseppe Finzi and Enrico Tazzoli rescued sailors of the sunken German commerce raider Atlantis.

On 26 November 1942 Giuseppe Finzi sailed for a ninth patrol to Brazil; but mechanical problems required return to base on 10 December.

Renamed UIT21 in German service, she was scuttled at Le Verdon-sur-Mer on 25 August 1944 to prevent her capture by advancing Allied forces.