[1]: 60 On September 1, five Brazilian ironclads, Bahia, Barroso, Lima Barros, Rio de Janeiro and Brasil began bombarding the batteries at Curuzú, which continued the next day.

That is when the Rio de Janeiro hit two mines and sank immediately along with her commander Américo Brasílio Silvado, and 50 sailors.

Simultaneously, 8,391 men of the Brazilian 2nd Corps, under the command of Manuel Marques de Sousa, then Viscount of Porto Alegre, attacked the Paraguayan batteries at Curuzú, south of the main stronghold of Humaitá on the shores of Paraguay River.

[1]: 61 The Brazilian ironclad Rio de Janeiro had a hole blown in her bottom by a contact mine, and sank almost immediately – the greater part of her crew, together with her captain, being drowned.

[2] President Francisco Solano López decimated the 10th Infantry Battalion on 10 September 1866, killing 63 men.