Meanwhile, Alvaro, believing Leonora to be dead, has joined the Spanish army under the name of Don Federico Herreros and has distinguished himself for bravery ("La vita è inferno all'infelice ... O tu che in seno agli angeli" – "Life is a hell to an unhappy man." ... "Oh, you who dwell with the angels"). He is interrupted by cries for help and rescues a man from two assassins. It is Don Carlo, who has newly joined the same regiment, also under an assumed name: Don Felix Bornos. The two become friends and march off side by side to fight in the Battle of Velletri, a historical event which occurred in 1744.