Battle of Caseros The Battle of Caseros was fought near the town of Caseros , more precisely between the present - day railway stations of Caseros and Palomar ( the actual battlefield is now occupied by the " Colegio Militar de la Nación " ( National Military College ) , a military academy ) in Buenos Aires Province , Argentina , on 3 February 1852 , between the Army of Buenos Aires commanded by Juan Manuel de Rosas and the Grand Army ( " Ejército Grande " ) led by Justo José de Urquiza . The forces of Urquiza , " caudillo " and governor of Entre Ríos , defeated Rosas , who fled to the United Kingdom . This defeat marked a sharp division in the history of Argentina . As provisional Director of the Argentine Confederation , Urquiza sponsored the creation of the Constitution in 1853 , and became the first constitutional President of Argentina in 1854 . Rosas had declared war on Brazil in 1851 , which led to the signing of a treaty , on 21 November 1851 , among the governments of Entre Ríos , Corrientes , Uruguay and the Brazilian Empire . In compliance with the treaty , Urquiza led a joint army and crossed Morón creek , positioning his forces in Monte Caseros . The Brazilian Empire contributed with 3 , 500 troops but the bulk of the Brazilian Army remained out of the battlefield . The battle . Rosas ' forces comprised 10 , 000 infantry troops , 12 , 000 cavalrymen and 60 guns . Among his captains were Jerónimo Costa , who defended Martín García island from the French in 1838 ; Martiniano Chilavert , a former opponent of Rosas who defected when his fellows allied themselves with foreigners ; Hilario Lagos , veteran from the campaign against the Indians of 1833 . Due to desertion , especially that of General Ángel Pacheco and poor morale , several historians and military analysts reckon that for Rosas the battle was lost even before it started . However , his opponent also suffered from desertions like that of the " Regimiento Aquino " , a regiment composed by soldiers loyal to Rosas , who murdered their captain Pedro León Aquino and joined the Rosist army . Urquiza ' s army was 24 , 000 - men strong , among them 3 , 500 Brazilians and 1 , 500 Uruguayans , and 50 guns . Only the Brazilians were professional soldiers . Urquiza did not conduct the battle : each chief was free to fight as they saw fit . Urquiza himself led a charge against the enemy left in front of their cavalrymen from Entre Ríos . Meanwhile the Brazilian infantry , supported by a Uruguayan brigade and an Argentine cavalry squadron seized the " Palomar " , a circular building near the right of the Rosist line and used for pigeon breeding , extant to this day . After both flanks collapsed only the center under Chilavert ' s command continued the fighting , reduced to an artillery duel that lasted until he ran out of ammunition . The whole battle lasted about three hours , after which Rosas was wounded in a hand and fled ; he wrote a resignation , and a few hours later he boarded the British frigate HMS " Centaur " towards exile in Southampton . Aftermath . Urquiza ' s triumph terminated the 20 - years term of Rosas as Governor of Buenos Aires and " de facto " Argentina ' s ruler . Within a few days , Urquiza ' s troops entered the city of Buenos Aires without further resistance . However , he revealed himself as a ruthless conqueror : all surviving soldiers from " Regimiento Aquino " and Chilavert himself were executed without a trial . The President of the Superior Tribunal , Vicente López y Planes , was appointed interim governor .