The Paraguayan War, also known as the War of the Triple Alliance, was a South American war that lasted from 1864 to 1870. It was fought between Paraguay and the Triple Alliance of Argentina, the Empire of Brazil, and Uruguay. It was the deadliest and bloodiest inter-state war in Latin American history. Paraguay sustained large casualties, but the approximate numbers are disputed. Paraguay was forced to cede disputed territory to Argentina and Brazil. The war began in late 1864, as a result of a conflict between Paraguay and Brazil caused by the Uruguayan War. Argentina and Uruguay entered the war against Paraguay in 1865, and it then became known as the "War of the Triple Alliance."
The Battle of Curupayty was a key battle in the Paraguayan War. On the morning on 22 September 1866, the joint force of Brazilian, Argentine, and Uruguayan armies attacked Paraguayan fortified trenches on Curupayty. The Paraguayans were led by general José Eduvigis Díaz. This position was held by 5,000 men and 49 cannons, some of them in hidden places out of the attackers view. The Imperial Brazilian Navy gave support to the 20,000 assailants, but the ships had to keep some distance from the guns at the fortress of Humaitá, which led to the lack of accuracy and impact of the ship's fire. The navy's failure was crucial at the later ground battle result.
The Battle of Tuyutí was a Paraguayan offensive in the Paraguayan War targeting the Triple Alliance encampment of Tuyutí. It is considered to be the bloodiest battle ever in South America. The result of the battle was an Allied victory, which added to the Paraguayan troubles after the loss of its fleet in the Battle of Riachuelo.
In the Paraguayan War, the Battle of Yatay was fought on August 17, 1865, between the troops of the Triple Alliance and the soldiers of Paraguay near Paso de los Libres, Corrientes, Argentina.
The military history of Brazil comprises centuries of armed actions in the territory encompassing modern Brazil, and the role of the Brazilian Armed Forces in conflicts and peacekeeping worldwide. For several hundreds of years, the area was the site of intertribal wars of indigenous peoples. Beginning in the 16th century, the arrival of Portuguese explorers led to conflicts with the aboriginal peoples; a notable example being the revolt of the Tamoio Confederation. Sporadic revolts of African slaves also marked the colonial period, with a notable rebellion led by Zumbi dos Palmares. Conflicts were encountered with other European nations as well – two notable examples being the France Antarctique affair, and a conflict with the Netherlands in the early 17th century over control of much of the Northeast. Although Portugal retained its possessions during conflicts with other nations, it lost control of the colony after the Brazilian war of Independence, which led to the establishment of the Empire of Brazil.
The Uruguayan War was fought between Uruguay's governing Blanco Party and an alliance consisting of the Empire of Brazil and the Uruguayan Colorado Party, covertly supported by Argentina. Since its independence, Uruguay had been ravaged by intermittent struggles between the Colorado and Blanco factions, each attempting to seize and maintain power in turn. The Colorado leader Venancio Flores launched the Liberating Crusade in 1863, an insurrection aimed at toppling Bernardo Berro, who presided over a Colorado–Blanco coalition (fusionist) government. Flores was aided by Argentina, whose president Bartolomé Mitre provided him with supplies, Argentine volunteers and river transport for troops.
Manuel Luís Osório, Marquis of Erval was a Brazilian military officer, monarchist and politician. A member of the Imperial Army at the age of fifteen, he climbed all the posts of the military hierarchy of his time thanks to the soldier attributes that consecrated him as "The Legendary". He participated in the main military events of the late nineteenth century in the Río de la Plata region and is considered a hero of the Paraguayan War. He was declared patron of the Cavalry Branch of the Brazilian Army in 1962.
The siege of Humaitá was a military operation in which the Triple Alliance flanked, besieged and captured the Fortress of Humaitá, a Paraguayan stronghold that was referred to as the Gibraltar of South America. It fell on 26 July 1868. It can be considered the key event of the Paraguayan War since the fortress had frustrated the allied advance into Paraguay for more than two years. However it did not surrender as the defenders escaped, most of them to fight another day.
The so-called Ejército Grande, also called the Ejército Grande Aliado Libertador, was the coalition army that in 1852, under the command of the governor of Entre Ríos, Justo José de Urquiza, invaded the provinces of Santa Fe and Buenos Aires and defeated Juan Manuel de Rosas's army, which until that moment was in command of the foreign relations of the Argentine Confederation.
The siege of Uruguaiana was an engagement in the Paraguayan War that began in late August 1865, and ended on 18 September that year when the Paraguayans were forced to surrender due to low food supplies. Paraguayan forces surrendered in spite of President López's order to the Paraguayan commander, Colonel Estigarribia, not to do so. After the allied victory at Uruguaiana, Lopéz withdrew his army from Argentina and Brazil.
The Battle of Pehuajó, also known as Battle of Corrales or Battle of Itati was fought during the Paraguayan War on 31 January 1866.
Events in the year 1866 in Brazil.
The Battle of Boquerón was fought on 16 July 1866 and the Battle of Sauce on 18 July 1866, between an allied force of Uruguayans, Brazilians, and Argentines on one side and Paraguay on the other in the Paraguayan War. The Spanish-born Uruguayan officer León de Pallejas (1816–1866) and the Paraguayan officer Elizardo Aquino were killed in the battle.
The Second Battle of Tuyutí was fought on 3 November 1867 between the Paraguayan Army and a smaller allied Brazilian-Argentine force. The Paraguayans lost twice as many soldiers as the allies and were defeated.
The Battle of Paso de Patria was a battle of the Paraguayan War, which took place between April 16 to 23, 1866, on the banks of the Paraná River, in the then fortified position in Paso de Patria, in which the Empire of Brazil emerged victorious. It took place simultaneously with the Battle of Itapirú, during the so-called "crossing of the Paraná River".
The Assault of Paso Cidra was an allied military operation during the Paraguayan War, which took place on May 20, 1866, in Estero Bellaco, Paraguay. The action consisted of the assault by Brazilian forces of the 2nd Infantry Battalion, under the command of Vanderlei Lins, subordinate of Uruguayan general Venâncio Flores, to a Paraguayan entrenched position, defended by men of Lieutenant Colonel Avelino Cabral. The operation was successful, with taking the position and clearing the path for the Allied march.
José Pons de Ojeda, later known as León de Pallejas, was a Uruguayan general of Spanish origin who participated in the First Carlist War, the Argentine Civil Wars and the Paraguayan War.
Antonio de la Cruz Estigarribia was a Paraguayan Lieutenant colonel who was notable for his service in the Paraguayan War. He served as one of the main Paraguayan commanders during the Invasion of Rio Grande do Sul, organizing the Battle of São Borja and the Siege of Uruguaiana before his surrender.
The Corrientes campaign or the Paraguayan invasion of Corrientes was the second campaign of the Paraguayan War. Paraguayan forces occupied the Argentinian city of Corrientes and other towns in Corrientes Province. The campaign occurred at the same time as the Siege of Uruguaiana.
The Humaitá campaign or the Cuadrilátero campaign was the third, longest and deadliest campaign of the Paraguayan War. The campaign lasted from 16 April 1866 to 5 August 1868. After the initial Paraguayan success in the Mato Grosso campaign and its failure in the Corrientes campaign, the armed forces of the Triple Alliance, Argentina, the Empire of Brazil and Uruguay, invaded the south of Paraguay. At a very short distance, they found the Paraguayan defensive device made up of four fortifications, the so-called "Cuadrilátero", which obstructed the passage to Asunción both by land and by the Paraguay River. A long series of battles cost huge numbers of casualties on both sides, with operations coming to a complete halt after the allied defeat at the Battle of Curupayty. Casualties on both sides were even higher from disease than from battle due to a cholera epidemic which was added to the appalling food and sanitary conditions.
Paraguay 
