Mariz e Barros temporarily commanded the yacht Paraibano, and effectively the gunboat Campista and the corvettes Belmonte, Recife, and the battleship Tamandaré, gaining prominence on the battlefield during the Uruguay Campaign, where he carried out a successful raid on Paysandú and another against the Sevastopol fort.

He was awarded the Order of the Rose after accompanying emperor Pedro II on his journey to the North and the Legion of Honor for saving a French barge that was about to sink on the rocks of the Fort of Laje [pt].

In his honor, the Municipal Chamber of Rio de Janeiro changed the name of Nova do Imperador Street, in the neighborhood of Tijuca, to Mariz e Barros on 16 November 1874.

[2][3] While commanding a naval division and the corvette Belmonte, Mariz e Barros escorted emperor Pedro II on his trip to Northeastern Brazil and was decorated with the habit of the Order of the Rose.

[6] With the beginning of the Uruguayan Campaign, Mariz e Barros was assigned to the battlefront, gaining notoriety by making a successful raid on the stronghold of Paysandú.

He also received the support of a detachment of one hundred soldiers from the First Infantry Battalion, commanded by lieutenant Eduardo Emiliano da Fonseca, again mounting a successful offensive against the Sebastopol fort.

[2] After a short period of firing at the fort, the battleship returned close to the Paraguayan barge, ordering the force on land to begin boarding the vessel.

However, when the battleship returned to its place in the line of battle, a shot from the fort hit one of the chains that protected one of the portholes, penetrating the casemate and damaging the vessel.

[2] According to reports, Mariz e Barros had "the left leg separated from the thigh at the joint, all the tendons and nerves distended and ruptured, and the bone fragments of the condyles of the femur attached to the tissues".