[1] For surface running, the boats were powered by two 600-brake-horsepower (447 kW) diesel engines, each driving one propeller shaft.

On June 29, 1940 Beilul made a reconnaissance mission near Alexandria surveying British Mediterranean Fleet.

In the evening of July 7, 1940 while patrolling in the waters off Crete, in approximate position 32°40′N 28°10′E / 32.667°N 28.167°E / 32.667; 28.167, Beilul sighted and attacked on the surface from about 1000 yards an enemy destroyer, part of the British Mediterranean Fleet.

The submarine then had to withstand a series of depth charge attacks which caused significant damage, forcing her to abort the mission and return to base.

[6] On January 8, 1941, lurking in the waters north of Kasos, she sighted a formation composed of five merchant ships and three escorts.

On the evening of December 1, Beilul, now under command of captain Francesco Pedrotti, was attacked on the surface by a Sunderland flying boat.

The crew of the submarine managed to beat back the attack with her anti-aircraft weapons and forced the aircraft to turn away, visibly damaged and on fire.

On June 12, 1943, now under command of captain Pasquale Beltrame, Beilul, patrolling off Capo Passero, sighted a formation of three British J-class destroyers.

On September 9, 1943, Beilul while still under repair and immobilized, was captured by the Germans, who turned it into fuel storage barge.