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

After Italy's entrance into World War II, Dagabur, under the command of Captain Domenico Romano, was engaged in various defensive missions, mainly anti-submarine, in the Gulf of Taranto and off the coasts of Tunisia and Libya.

These three submarines were a part of the screening force covering the main Italian battle formation involved in Operation "Gaudo".

There was no news of the result of this attack, and it's likely the cruiser was damaged, but hours later, HMS Bonaventure was torpedoed again, this time, by the submarine Ambra and sunk with a loss of 23 officers and 115 other members of the crew.

On December 14, 1941, Dagabur, now under the command of Captain Alberto Torri, intercepted while surfaced, and launched two torpedoes at an unknown unit, and immediately disengaged by diving.

At the beginning of August 1942, Dagabur, now under the command of Captain Renato Pecori, left Cagliari and was sent to patrol an area between Ibiza and Mallorca and the northern coast of Algeria.

Dagabur attempted to maneuver into approach on the surface but was spotted and attacked and rammed by the destroyer HMS Wolverine and sank with all hands in position 37°18′N 1°58′E / 37.300°N 1.967°E / 37.300; 1.967 on August 12.