Later, in 1910, Sauro became an employee of the shipping company Zuttiati, connecting ports in Istria and Dalmatia to San Giorgio di Nogaro and Cervignano del Friuli.

Tino Gavardo, Pio Riego Gambini and Nazario Sauro were the most renowned of those who promoted Istrian unification to the Kingdom of Italy.

When Italy joined the effort in 1915, Sauro was a volunteer in the Italian Navy, assigned to a torpedo unit, accomplishing over 60 missions over a period of 14 months.

On 30 July of that year, Sauro's boat was sent over to carry out sabotage in the Hungarian port of Fiume (now Rijeka in Croatia), but it crashed into a rock in the Kvarner Gulf.

Sauro was recognized and placed on trial for his previous act of treason, and, after facing a military tribunal in Pola (now Pula in Croatia) was sentenced to death and hanged.