Paraguayan War

The Paraguayan War, also called the War of the Triple Alliance, was fought from 1864 to 1870 between Paraguay and an alliance of the Empire of Brazil, Argentina and Uruguay. It was the deadliest war between states in Latin American history. Paraguay was utterly defeated, lost a large share of its population and gave up disputed territory to its two large neighbours.

After independence from Spain and Portugal, the states of the River Plate basin disputed their borders and competed for influence in Uruguay, which lay between Brazil and Argentina. Landlocked Paraguay depended on the Paraná and Paraguay rivers for access to the sea. Under its presidents Carlos Antonio López and, from 1862, his son Francisco Solano López, it had built a strong army and a centralised state.

In 1864 Brazil intervened in Uruguay's civil war in support of the Colorado party against the ruling Blanco government, which was friendly to Paraguay. Solano López had warned that he would treat such an intervention as a threat to the regional balance.

In November 1864 Paraguay seized a Brazilian steamer on the Paraguay River and in December invaded the Brazilian province of Mato Grosso. When Argentina refused permission for Paraguayan troops to cross its territory to reach southern Brazil and Uruguay, Paraguay declared war on Argentina and in April 1865 occupied the city of Corrientes. Brazil, Argentina and the new Colorado government of Uruguay then signed the Treaty of the Triple Alliance on 1 May 1865, agreeing not to make peace while Solano López remained in power. The treaty also set out territorial gains for Argentina and Brazil.

The Paraguayan offensive soon failed. On 11 June 1865 the Brazilian navy destroyed much of the Paraguayan fleet at the Battle of Riachuelo, and a Paraguayan column that had invaded Rio Grande do Sul surrendered at Uruguaiana in September.

From 1866 the allies, under the Argentine president Bartolomé Mitre and later the Brazilian Marquis of Caxias, invaded Paraguay. The Battle of Tuyutí in May 1866 was one of the bloodiest in the continent's history. In September the allies suffered a heavy defeat attacking the trenches at Curupayty, and the fighting stalled before the great river fortress of Humaitá. Brazil, which bore most of the allied effort, sent ironclads past the fortress in February 1868, and Humaitá fell in July. The allies occupied the capital, Asunción, on 1 January 1869.

Solano López withdrew to the interior and continued to resist, conscripting old men and boys as his army shrank. At Acosta Ñu in August 1869, many of the Paraguayan dead were children. Hunger and disease devastated the civilian population. On 1 March 1870 Solano López was killed by Brazilian troops at Cerro Corá, ending the war.

The scale of Paraguay's losses is one of the most debated questions in the region's history. Estimates of the pre-war population range widely, and so do estimates of the deaths. One influential study concluded that perhaps 60 to 70 per cent of Paraguay's population of around 420,000 to 450,000 died, with adult men suffering most; other scholars argue for lower figures. Whatever the exact number, a census taken just after the war showed that women greatly outnumbered men. Brazil lost an estimated 50,000 soldiers or more, and Argentina and Uruguay suffered thousands of deaths.

Brazilian and Argentine troops remained in Paraguay until 1876. Paraguay ceded to Brazil the lands it had disputed in the north and to Argentina territory in Misiones and the Chaco, losing in all about 30 per cent of the land it had claimed. Its economy was ruined and its politics unstable for decades. In Brazil, the war raised the prestige of the army, which later played a leading part in the overthrow of the monarchy in 1889.

Our 1815 map shows Paraguay soon after independence, and the 1878 map shows the reduced Paraguay of the post-war settlement.