[3] In 1938 she was reassigned to Tobruk, and in 1940 she returned to Italy, and was assigned to 46th Squadron (IV Submarine Group) based first at Taranto and then at Augusta.

At the beginning of the World War II, from 8 to 16 August 1940, Dessiè, under command of Captain Fausto Sestini, patrolled the waters between Gaudo and Cerigotto, just off the coast of Crete.

[4] At the end of the month, she was again deployed, now under command of Captain Adriano Pini, this time off Malta, with the task of intercepting the ships of British Operation Collar.

[6] On 3 January 1942, Dessiè was sent to patrol an area south off Malta with the task of detecting and attacking any British naval forces that might attempt to intercept Italian convoy "M 43", bringing supplies to Libya.

In mid-June 1942, she was sent along with four other submarines, including Aradam and Ascianghi to patrol between Malta, Pantelleria and Lampedusa, with the task of intercepting a British convoy, part of Operation Harpoon.

On 11 August 1942, Dessiè, now under command of Captain Renato Scandola, was among eleven submarines deployed off the coast Tunisia between Scoglio Due Fratelli and Skerki Banks.

However, the steamship succeeded in restarting her engines and reaching Malta on 14 August after a short stop in Soussa, even though she was further damaged by German torpedo bombers.

In the evening of 13 August, she was bombed by an aircraft, that killed one crew member and wounded several others and caused damage to her batteries, which forced her to return to base.

On 18 November, Dessiè sailed from Messina, under command of Captain Alberto Gorini, to patrol an area off the coast of Bona, Algeria, and to attack enemy traffic around the ports of Philippeville and Bougie.

Only after the end of World War II was it was learned that Dessiè had been detected on the surface by airplanes at 14:05 on 28 November, about 10 miles (16 km) off Bona.