She engaged several Austrian wooden vessels in the melee, including ship of the line Kaiser, which rammed Re di Portogallo but inflicted no significant damage.

[1] The keel for Re di Portogallo was laid down at the William H. Webb Shipyard in New York City in December 1861; she and her sister were the only Italian ironclads to be built in the United States.

Persano claimed he was simply waiting on the ironclad ram Affondatore, en route from Britain, but his inaction weakened morale in the fleet, with many of his subordinates openly accusing him of cowardice.

[4] Rear Admiral Wilhelm von Tegetthoff brought the Austrian fleet to Ancona on June 27, in attempt to draw out the Italians.

Persano held a council of war aboard the ironclad Principe di Carignano to determine whether he should sortie to engage Tegetthoff, but by that time, the Austrians had withdrawn, making the decision moot.

The Minister of the Navy, Agostino Depretis, urged Persano to act and suggested the island of Lissa, to restore Italian confidence after their defeat at the Battle of Custoza the previous month.

[6] Re di Portogallo was at that time in the 3rd Division, along with the ironclads Terribile, Formidabile, and Regina Maria Pia, and the coastal defense ship Varese.

After spending the 18th unsuccessfully bombarding the Austrian fortresses, the Italians withdrew late in the day, preparing to launch another attack the following morning.

[7] The next morning, Persano ordered another attack; four ironclads would force the harbor defenses at Vis while Re di Portogallo and the rest of the fleet would attempt to suppress the outer fortifications.

Re di Portogallo initially had trouble getting her engines running, but after repairs were quickly made, she joined the rest of the fleet.

[8] Shortly before the action began, Persano decided to leave his flagship and transfer to Affondatore, though none of his subordinates on the other ships were aware of the change.

He failed to ram any Italian vessels on the first pass, so he turned back toward Persano's ships, and took Re d'Italia, San Martino, and Palestro under heavy fire.

[10] After the battle, Vacca replaced Persano; he was ordered to attack the main Austrian naval base at Pola, but the war ended before the operation could be carried out.

[1] By October 1871, Re di Portogallo had been stationed in La Spezia, along with Regina Maria Pia, San Martino, Castelfidardo, Affondatore, and the new ironclad Roma.