On the morning on 22 September 1866, the joint force of Brazilian, Argentine, and Uruguayan armies attacked Paraguayan fortified trenches on Curupayty.

Paraguay's biggest success in the ultimately disastrous war was limited because its military leader, Francisco Solano López, did not counterattack the defeated Allies.

Participating in the attack were the ships Brasil, Barroso, Tamandaré, Ipiranga, Belmonte, Parnaíba, Pedro Affonso, Forte de Coimbra, and the gunboats No.

[1]: 63–64 Bartolomé Mitre saw that the Imperial fleet had finished its cannonade and, assuming that the Paraguayan positions were destroyed, ordered the advance on land.

The Triple Alliance forces, recognizing their underestimation of Paraguay's defensive capabilities, adopted a more cautious approach to future engagements.

Open revolt against the war started in Argentina by January 1867, forcing President Mitre to send "The Army of Pacification" of 4,000 under Paunero's command.

[1]: 65  In general, the battle raised doubts about the feasibility of a swift victory, contributing to the war's prolongation and exacerbating the humanitarian crisis in the region.

Today, the Battle of Curupayty is commemorated as a symbol of Paraguayan resistance and national pride, while also serving as a reminder of the high cost of war.