In the Paraguayan War, the Battle of Yatay 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 Yatay was the first major land battle of the Paraguayan War, and most important of the war's second phase.
Background
Following the declaration of war by Paraguayan president Francisco Solano López on Argentina, the Paraguayans immediately attacked with two columns. The original plan was that the first column, commanded by Wenceslao Robles, would seize the town of Corrientes while 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, as this would prevent Brazilian expansion, a great concern of president López. The other column would then capture Corrientes, distracting Argentine forces and creating 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 later divert southeast and invade Uruguay. In response, a military alliance was signed on 1 May among Argentina, Uruguay and the Empire of Brazil.
Following the successful capture of Corrientes by the Paraguayans, Argentine general Wenceslao Paunero launched a daring attack – on 25 May – that recaptured the city. However, given the numerical superiority of the Paraguayans, Paunero chose to evacuate 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 advancing on the Uruguay River.
Argentine president Bartolomé Mitre put general Justo José de Urquiza, governor of the province of Entre Ríos, in charge of facing 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. Many future heroes of the Corrientes province, such as Santiago Baibiene and Plácido Martínez, were in that battalion.
Meanwhile, the naval Battle of Riachuelo took place. During the course of the battle the Imperial Brazilian fleet destroyed the Paraguayan squadron near the city of Corrientes. This loss prevented the Paraguayan column on the Paraná River from providing support to the forces on the Uruguay River.
Armies
On 5 May, after invading the northwest of the province of Corrientes, General Estigarribia sent colonel Pedro Duarte in front of a small advance column to control the bank of the Uruguay River. Duarte took the city of Santo Tomé. Estigarribia's forces followed up and met him there four days latter. The army then crossed the Uruguay River and entered the Brazilian province of Rio Grande do Sul. 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, Estigarribia's column was attacked and partially destroyed on the outskirts of São Borja, in the battle of Butuí. Some of the Paraguayan forces were stationed in São Tomé 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 on the grounds of being considered allies against Brazil (which Argentina had frayed relations with), were disbanded.
Uruguayan president and general Venancio Flores, fresh from his triumph over the Blanco party, marched to join Urquiza with 2,750 men. In addition, the Brazilian forces, commanded by lieutenant colonel Joaquim Rodrigues Coelho Nelly, numbering 1,200 men, were heading their way. They met on July 13. At the first meeting Flores was given the Line Cavalry Regiment "San Martín", with 450 men, plus one Uruguayan artillery squadron with 140 men. In total, Flores had 4,540 troops—not nearly enough to confront the Paraguayan columns.
Flores, Duarte and Estigarribia marched slowly to meet and engage in battle, while Paunero's 3,600 men began a march through swamps and rivers, swiftly crossing the southern province of Entre Ríos to join Flores. In addition, 1,400 cavalry soldiers from Corrientes under the command of general Juan Madariaga joined their forces. Finally, colonel Simeón Paiva, with 1,200 men, closely followed the column of Duarte.