Battle of Acosta Ñu The Battle of Acosta Ñu or Campo Grande was a battle during the Paraguayan War , where , on August 16 , 1869 , 20 , 000 men of the Triple Alliance fought Paraguayan forces made up of 6 , 000 soldiers , most of them children . Background . In the middle of 1869 , the Paraguayan Army was on the run and Asunción was under allied occupation . Francisco Solano López , the Paraguayan president , refused to surrender and fled , vowing to keep fighting to the end . The Brazilian commander Duque de Caxias suggested that the war was militarily over , but Dom Pedro II , the Brazilian Emperor , refused to stop the campaign until López surrendered . Caxias resigned due to illness and was replaced by the Emperor ' s son - in - law , Luís Filipe Gastão de Orléans , Count d ' Eu . Under the new command , the Brazilian Army continued the campaign in Paraguay until finally killing López in 1870 . With most adult Paraguayan males already killed or captured , López started to use children and elderly in the Army to keep the fight against the Alliance . Some children fought with fake beards to conceal their age . The beginning . Count d ' Eu and the main Allied troops advanced and took Caacupé on August 15 , where López was supposedly hiding ( he had actually fled to Caraguataí some days before ) . To block the Paraguayan Army from retreating to Caraguataí , d ' Eu sent a Brazilian cavalry division to the passage at Campo Grande . The division was reinforced later by the 2nd Brazilian Army Corps , along with Argentinian troops commanded by colonel Luis María Campos . The battle . The Allied troops met the rearguard of the Paraguayan forces at Acosta Ñu on August 16 . The battle started at 08 : 30 in the morning , with the 6 , 000 Paraguayans commanded by General Bernardino Caballero facing 20 , 000 Brazilian and Argentinian troops . Acosta Ñu ( which means " Big Field " ) is a vast plain of roughly , ideal for the Brazilian cavalry . However the cavalry was at the rear guard of the forces , and the initial charge was led by the Allied infantry . The battle would last eight hours , with the outnumbered Paraguayans providing a fierce resistance . After the first shots , the troops of General Caballero retreated to the other side of river Juquerí , where they had eight cannon and coverage . They set fire to the grass to hide their movements with smoke . The Allied infantry made the first charge to cross the river but was repelled . Count d ' Eu then ordered his artillery to open fire , which caused huge losses on the Paraguayan side . By then the Brazilian cavalry had finally reached the battlefield , and was able to cross the river and make a devastating charge against the Paraguayan position . General Caballero ' s troops defended using a classic infantry square formation with bayonets , but his troops still suffered huge losses . The Allied infantry charged again with bayonets , taking the eight cannon and the Paraguayan position . At the end 2000 Paraguayans were dead and 1200 captured . The Allied forces suffered 46 dead and 259 wounded . General Caballero fled along with part of his troops . The Battle in history . The battle of Acosta Ñu / Campo Grande was the last major battle in the war , which would finally end months later with the death of López . The battle is depicted in the famous painting Batalha de Campo Grande by Pedro Américo , and in the book Recordações de Guerra e de Viagem by famous Brazilian writer Visconde de Taunay , who took part in the battle . Caballero would surrender later , and like many other Paraguayan officers in this situation was taken prisoner to Rio de Janeiro , where he lived for some years at a family house . He later went on to be President of Paraguay ( 1880 – 1886 ) . Manoel Deodoro Da Fonseca led one of the Brazilian infantry battalions and was later the first President of Brazil ( 1889 – 1891 ) . In Paraguay , Children ' s Day is celebrated on August 16 . It is a national holiday to commemorate the memory of the children who lost their lives in the Battle of Acosta Ñu / Campo Grande .