Triple Alliance War

Paraguayan War
Clockwise from top left: Uruguayan artillery in the Battle of Boquerón, Brazilian soldiers kneel in a religious procession, Brazilian troops in Nova Palmira, Brazilian troops in Tayi, officers of the Argentine Army, officers of the Imperial Brazilian Army.
Date 12 October 1864 – 1 March 1870 Location South America; Paraguay, Brazil and Argentina Result Allied victory Treaty of the Triple Alliance ended Loizaga – Cotegipe Treaty between Brazil and Paraguay Machaín-Irigoyen Treaty between Argentina and Paraguay Free navigation in the Platine region Territorial changes Brazil definitively gained the disputed territories north of the Apa River, now part of Mato Grosso do Sul State. Argentina definitively gained the disputed Misiones Province and all the disputed lands south of the Pilcomayo River now constituting Formosa Province. Paraguay permanently lost its claims to lands amounting to almost 40% of its prewar claimed territories.
Belligerents
Triple Alliance:  Brazil  Argentina  Uruguay	Paraguay
Commanders and leaders
Emperor Pedro II Duke of Caxias Count of Eu Bartolomé Mitre Domingo Faustino Sarmiento Venancio Flores	Francisco Solano López † José E. Díaz † Domingo Francisco Sánchez †
Strength
139,000 Brazilians 30,000 Argentines 5,583 Uruguayans Total: 174,583	150,000 Paraguayans 80,000 official troops and 70,000 militia and armed civilians
Casualties and losses
Total: 140,000 soldiers and civilians Empire of Brazil: 50,000 soldiers 50,000 civilians Republic of Argentina: 18,000 soldiers 13,000 civilians Oriental Republic of Uruguay: 3,100 Uruguayans	300,000 soldiers and civilians
Total: 440,000 dead

Allied victory

Total: 140,000 soldiers and civilians

Republic of Argentina:

Oriental Republic of Uruguay:

The Paraguayan War, also known as the War of the Triple Alliance and the Great War in Paraguay, was a South American war fought from 1864 to 1870 between Paraguay and the Triple Alliance of Argentina, the Empire of Brazil, and Uruguay. With an estimated 400,000 deaths, the war was the deadliest and bloodiest in Latin America's history. It particularly devastated Paraguay, which suffered catastrophic losses in population – almost 70% of its adult male population died, according to some counts – and was forced to cede territory to Argentina and Brazil. According to some estimates, Paraguay's pre-war population of 525,000 was reduced to 221,000, of which only 28,000 were men.

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 war ended with the total defeat of Paraguay. After it lost in conventional warfare, Paraguay conducted a drawn-out guerrilla resistance, a disastrous strategy that resulted in the further destruction of the Paraguayan military and much of the civilian population through battle casualties, hunger and diseases. The guerrilla war lasted 14 months until President Francisco Solano López was killed in action by Brazilian forces in the Battle of Cerro Corá on March 1, 1870. Argentine and Brazilian troops occupied Paraguay until 1876. Estimates of total Paraguayan losses range from 21,000 to 200,000 people. It took decades for Paraguay to recover from the chaos and demographic losses.

Since their independence from Portugal and Spain in the early 19th century, the Empire of Brazil and the Spanish-American countries of South America were troubled by territorial disputes. All nations in the region had lingering boundary conflicts with multiple neighbors. Most had overlapping claims to same territories. These issues were questions inherited from their former metropoles, which, despite several attempts, were never able to resolve them satisfactorily. Signed by Portugal and Spain in 1494, the Treaty of Tordesillas was proved ineffective in the following centuries as both colonial powers expanded their frontiers in South America and elsewhere. The outdated boundary lines did not represent actual occupation of lands by Portuguese and Spanish.

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