Battle of Yatay The Battle of Yatai was fought on August 17 , 1865 between the troops of the Triple Alliance ( Argentina , Brazil and Uruguay ) and the soldiers of Paraguay near Paso de los Libres , Corrientes , Argentina . The Battle of Yatai was the first major land battle of the war , and most important of the war ' s second phase , the battle was fought in the territory of Corrientes . Background . Following the decalaration of war by Paraguayan president / dictator Francisco Solano Lopez on the state of Argentina the Paraguayans immediately attacked with two columns . The original plan was that the first column , commanded by Wenceslao Robles , would seize Corrientes . A second column of 12 , 000 men commanded by Antonio de la Cruz Estigarribia would then advance to the east of Corrientes and capture Brazilian possessions on the Uruguay river . The primary focus of this invasion plan was the capture of Brazilian possessions because this would prevent alleged Brazilian expansionsionism which was a great concern of President Lopez . The other column would then capture Corrientes distracting Argentine armed force and create a lifeline between Paraguay and the Atlantic Ocean . This plan was later revised so that two thirds of the assault force would attack Corrientes and latter divert southeast and invade Uruguay . In response , on May 1 a military alliance was signed between Argentina , Uruguay and the Empire of Brazil . Following the successful capture of Corrientes , Argentine General Wenceslao Paunero launched a daring attack – on May 25 – which recaptured the city . But , given the enormous numerical superiority of the enemy he chose to evacuated the city and its civilians two days later and head to the southwest of the province . Only after having evacuated Corrientes did Paunero learn that the Paraguayans were making progress on the Uruguay River . Argentine President Bartolomé Mitre instructed general Urquiza , governor of the province of Entre Ríos , to face the Paraguayan column . Urquiza called on his aid Paunero , who had retreated to Esquina . These forces were joined by a battalion of volunteers from Corrientes , led by Colonel Desiderio Sosa , who had participated in the reconquest of Corrientes , in the battalion there were many future heroes of the History of Corrientes Province such as Santiago Baibiene and Plácido Martínez . Meanwhile , the naval Battle of Riachuelo took place , during the course of the battle the Brazilian fleet destroyed the Paraguayan squadron near the city of Corrientes . This loss prevented the Paraguayan column Paraná River fom providing support to the forces on the Uruguay River . Armies . Having invaded the northwestern province of Corrientes , General Estigarribia sent May 5 Colonel Pedro Duarte in front of a small advance column to control the bank of the Uruguay River . Duarte took the city of Santo Tome Estigarribia ' s forces followed up and met him there four days latter . The army then crossed the Uruguay River and entered the state of Rio Grande do Sul , Brazil . They left behind them the column of Duarte , with more than 3 , 000 soldiers to defend Uruguay . Estigarribia advanced unopposed to the south , taking on São Borja and Itaqui . In the meantime , the Estigarribias ' s column was attacked and partially destroyed on the outskirts of São Borja , in combating Mbuty . Some of the Paraguayan forces were stationed in Sao Tome and São Borja while Duarte was heading south . Urquiza ordered Paunero to join him in Concordia , but the leader delayed the completion of Urquiza ' s orders . On June 4 the troops of Urquiza who refused to fight the Paraguayans , because they considered them allies against Brazil which Argentina had frayed relations with , were disbanded . General Venancio Flores , president of Uruguay fresh from his triumph over the white party or " blancos " , marched to join Urquiza with 2 750 men . Also the Brazilian forces , commanded by Lieutenant Colonel Joaquim Rodrigues Coelho Nelly , composed of 1 , 200 men , were heading their way . They met on July 13 . At the 1st meeting Flores was given the Line Cavalry Regiment " San Martín " , with 450 men , plus the artillery squadron East with 140 men . In total , Flores had 4 , 540 men , not nearly enough to confront the Paraguayan columns Flores , Duarte and Estigarribia marched slowly to meet and make battle , while with 3 , 600 men Paunero began a rapid march through swamps and rivers , rapidly crossing the southern province of Entre Rios to join Flores . In addition 1 , 400 of correntina cavalry under General Juan Madariaga joined their forces . Finally , Colonel Simeon Paiva , with 1 , 200 men , followed closely by the column of Duarte . Estigarribia had a chance to destroy all his enemies one by one , but missed . He also disobeyed orders from Lopez , who ordered him continue on his way to Alegrete : On August 5 , he went to Uruguayana and ordered his troops to reorganize and supply themselves . Brazilian forces of General David Canabarro , too few to attack the column of 5 , 000 men Estigarribia , were limited to camp near the city without being attacked by the Paraguayans . On August 2 , Duarte occupied the village of San José de Restoration , now the town of Paso de los Libres . A week later , he advanced and was defeated suffering 20 casualties in the battle of Chap Kish . Given the news that all enemy forces were in pursuit , Duarte sought help from his superior , General Estigarribia , who sent him to answer : Insulted , Duarte was prepared to give battle without any help . On August 13 Paunero avoided the army of Duarte and joined Flores whose forces then numbered 12 , 000 men , nearly four times the force of Duarte . Duarte moved away from Paso de los Libres and took position on the banks of the stream Yatay , near the village . There was a brief encounter on the afternoon of August 16 , and at dusk , the two armies were facing each other from half a mile off . The Battle . Both the Yatay and Uruguay rivers had recently flooded , leaving most of the battlefield flooded . Most Paraguayan infantry forces were entrenched among trees and ditches in the area of the nearby village estates , and were protected by a mud that covered the frontal approach , but leaving the stream behind them made it impossible to retreat in the case of a defeat , which was considered very likely Duarte . Duarte forces consisted of 1 , 980 infantry and 1 , 020 cavalry , with no artillery . The Allies had in total 5 , 550 foot soldiers , 5 , 000 cavalry and 32 pieces of artillery . Among the leaders of the allied army chiefs were experienced commanders Flores and Paunero , Lion Palleja , Ignacio Rivas , Enrique Castro and José Gregorio Suárez and Argentines Juan Bautista Charlone , José Miguel Arredondo , José Giribone Ignacio Segovia , Joaquin Viejobueno , Leopoldo Nelson , Simeon Paiva and Madariaga . The battle began at ten o ' clock , with a hasty attack on the Paraguayan positions by the Palleja Infantry Division . Duarte took advantage of the mistake and countered with almost all his cavalry , causing hundreds of casualties and forcing them to retreat . Faced with an increasingly bad situation , the cavalry division of Segovia attacked the Paraguayan cavalry , supported by Castro ' s eastern and Suarez . For two hours the battle was fought exclusively with cavalry . Duarte ordered a withdrawal maneuver , which finally enabled the Allied infantry into action , and although their ( the allies ) numerical superiority was overwhelming , the Paraguayans fought back with tenacity . When the battle was almost lost , Duarte tried a desperate cavalry charge , with the result that his horse was killed . Paunero himself demmanded Duarte to surrender , which he finally agreed to do . A final Paraguayan force of the infantry under Lt . Zorrilla , crossed the stream Yatay and was charged by a cavalry attack of Suarez and Madariaga , who attacked from the rear . A few hundred Paraguayan soldiers swam the river Uruguay , while the rest were killed or taken prisoner . In total , they suffered 1 . 500 dead and 1 , 600 prisoners , including 300 wounded . Consequences . Among the prisoners , Flores found several dozen soldiers from Uruguay , Blanco Party supporters who had taken refuge in Paraguay , and then tried to wrest power in Uruguay from the hands of the Flores ' forces . Flores ordered their execution as traitors . On September 18 , after having assured the representatives of Emperor that he would not surrender and would rather be buried under the rubble of Uruguayana , General Estigarribia surrendered almost without fighting anyway . Soon after , the Paraguayan forces occupying the abandoned city of Corrientes , retreated to the north , and soon to Paraguay . Virtually all the rest of the war was fought in the territory of Paraguay until the country ' s complete defeat in 1870 , after losing 70 % of its adult male population . A street in the city of Buenos Aires , in the district of Caballito , recalls this battle .