[1][2] Appointed captain in 1847, in 1848 he was part of the expeditionary force of 15,000 men that the constitutional government of Carlo Troya sent to Lombardy, under the command of Guglielmo Pepe to help the Kingdom of Sardinia in the First Italian War of Independence.

After the recall of the expeditionary force by King Ferdinand II Luigi Mezzacapo joined his brother Carlo and numerous other soldiers of the Sicilian army including Guglielmo Pepe, Enrico Cosenz, it:Cesare Rosaroll, Alessandro Poerio and it:Girolamo Calà Ulloa in besieged Venice where he distinguished himself in the defense of the city at the fort of Brondolo.

[6] After the fall of Rome Mezzacapo did not return to Naples but went into exile, first to Malta, and then Piedmont to where with his brother Carlo he created the "Military library for the use of Italian youth" and the " Rivista Militare" in 1856.

In March 1861, taking the place of it:Ferdinando Augusto Pinelli, he commanded the siege and finally conquered the fortress of Civitella del Tronto, the last bastion of the Bourbon forces.

[10] He was twice invited to return to the position of Minister of War, but refused on both occasions as he did not believe that parliament would agree the military budgets he felt were necessary to press forward with the modernisation of Italy’s armed forces.