After undergoing a brief training, from 27 August through 3 September 1937, she carried a special mission in connection with the operations of the Spanish Civil War.

In 1938 she was reassigned to La Spezia and in 1940, in view of her limited usage, was moved to Massawa and became part of the 82nd Squadron (VIII Submarine Group) of the Red Sea Flotilla.

On June 10, 1940, in the afternoon, she left Massawa under command of captain Dante Morone to begin her first war mission to operate in an area about eight miles east of Port Sudan.

It was also difficult to identify the reference points along the shoreline, and that presented a bigger danger since the area Macallé had to cross was littered with islets, sandbanks, reefs and rock outcrops.

As corrective measures were not taken, on June 14, 1940, all officers and almost all crew developed symptoms of chloromethane poisoning, including some cases of hallucinations.

As a result, the submarine crew found itself on an isolated island with scarce supplies and without the base knowing their position, and the fact that Macallé sank.

Since it would be impossible to survive for a long time on a deserted island, and not willing to surrender to the British, it was decided to send out a volunteer party to try to reach an Italian outpost on the coast of Eritrea.

In the evening of June 15, three men, Elio Sandroni, Torchia and Costagliola Paolo left on a small sailboat.