The Battle of Curuzu happened between September 1 and September 3 in 1866 in the context of Paraguayan War. After the first Battle of Tuiuti, won by the Allies on May 24 in 1866, commander of the reserves Mitre took ten thousand men brought by the baron of Porto Alegre and decided to attack the batteries in the Curuzu Fort and Fort Curupaiti, south of the main stronghold of Humaitá on the shores of Paraguay River.