 Porto Alegre assumed the command of the Brazilian army in Uruguaiana on 21 August 1865 . From the very beginning , he had an acrimonious relationship with Brazil 's allies Bartolomé Mitre , president of Argentina , and Venancio Flores , president of Uruguay , who led the armies of their respective nations . The years had not lessened Porto Alegre 's prejudice against Hispanic @-@ Americans ; on the contrary , his antagonism had increased . On 2 September , Flores suggested an immediate attack on Uruguaiana , an option rejected by Porto Alegre and Joaquim Marques Lisboa ( then Viscount and later Marquis of Tamandaré ) , the commander @-@ in @-@ chief of the Brazilian navy . Tamandaré was a first cousin of Porto Alegre ; their mothers were sisters . When Flores claimed that he could defeat the Paraguayan army alone , he was mocked by both Brazilian officers . 
