[1] The Paraguayan government ordered five battleships from European shipyards, four British (Meduza, Triton, Bellona, and Minerva) and one French (Nemesis).

Mariz e Barros died of complications after being wounded by shrapnel caused by a projectile coming from the battery of the Itapirú fortress that hit the battleship Tamandaré, which he commanded, and that also victimized 33 others who garrisoned it.

The ship arrived in Brazil on July 8, 1866, and was incorporated into the Navy on the 23rd, under the command of Captain lieutenant Silvino José de Carvalho Rocha.

Simultaneously, a fleet of six gunboats and speedboats under the leadership of Chief of Division Elisiário dos Santos, from another position in the fortress, dropped about 300 bombs on the target.

At the head of the squadron would be the 3rd Battleship Division, under the command of Frigate Captain Joaquim Rodrigues da Costa, composed of the Brasil, Tamandaré, Colombo, Bahia, and Mariz e Barros.

In the rear would be the 1st Battleship Division, under command of Captain Francisco Cordeiro Torres e Alvim, composed of the Cabral, Barroso, Herval, Silvado, and Lima Barros.

[7] To the total surprise of the Paraguayans, the passage of the imperial battleships took place close to their cannons instead of the more distant channel, however, this course was full of obstacles.

This passage occurred on February 19, 1868, with Mariz e Barros acting in the protection of the hospitals of Porto Elisiário,[8] which was between the two forts on the right bank of the Paraguay River.

[9] A few days later, on March 2, the ironclad was at the mouth of the Rio do Ouro, which flows into Paraguay, together with others that had passed Curupaití, when there was an attempt to board the vessels Cabral and Lima Barros by Paraguayans in canoes.

About a month later, the Mariz e Barros contributed to the bombardment of Humaitá in preparation for a major attack by the fleet and allied ground forces on the fortress that would occur in July.

The crossing took place on July 21, with the Cabral in the lead, but due to the ship's poor steering, it ended up ramming the Lima Barros, which was acting as support and had to stop for repair.

On that occasion, the Paraguayans returned heavy bombardment against the Mariz e Barros, which resulted in the death of Captain Augusto Neto de Mendonça and 12 wounded among the crew.

[14] After the conquest of Asunción, on January 1, 1869, the already worn-out large battleships, such as the Mariz e Barros, were no longer of much use in the conflict, with naval fighting taking place, from then on, in small, very narrow streams.