He signed the death warrants of his mother and sisters, but before Marshal-President Francisco Solano López could see the warrants carried out, Brazilian forces attacked his camp. Seriously wounded on February 28, 1870, the injured president was given a chance to surrender, but he refused, muttering the immortal words: “I die with my country.” One of the items recovered from his corpse was a ring engraved with the legend “Vencer o morir,” meaning “Win or die.”

That was to be the final act of the War of the Triple Alliance, aka the Paraguayan War, a grueling conflict spanning six years that killed — by bullets, disease and famine — 60 percent of the Paraguayan population, including more than 90 percent of the country’s adult men. Proportionally, it was the most destructive war of the modern era and had a profound regional impact; Brazil, Paraguay and Argentina have never been the same.

Theirs was a psychology of extremes, and they couldn’t stomach or even fathom any halfway choice or measure. —Thomas Whigham, professor of history, University of Georgia

Brazil, a monarchy that favored a tiny elite, was far and away the most powerful nation in the region; Argentina was a de facto oligarchy with big landowners sharing power; and landlocked Paraguay, which had a history of isolationism, followed an openly dictatorial model. Wedged between Brazil and Argentina was tiny Uruguay, where power vacillated between two opposing factions. When Brazil threatened Uruguay with military intervention in 1864, López, the Paraguayan dictator, issued an ultimatum. Ignoring the pesky Paraguayan, Brazilian troops invaded Uruguay, and Paraguay retaliated by seizing a Brazilian warship in Paraguayan waters, thus sparking the war. Curiously, Paraguay invaded Brazil to the north (they could have gone the other way) while Brazil marched south, ensuring that their favored candidate, Venancio Flores, came to power in Uruguay.

In early 1865, says Thomas Whigham, a history professor at the University of Georgia, “Lopez had the silly idea of asking Argentina for permission to transit through their territory to intercept the Brazilian advance.” When Argentina refused, López declared war on them too and shortly thereafter the Triple Alliance — of Brazil, Argentina and Uruguay — was signed in secret.

From there, war would play out in three distinct phases. The Paraguayan offensive kicked things off with several battles in both Brazil and Argentina, all of which resulted in Paraguayan defeats. The second phase, from 1866 to 1868, proved to be a conventional war of attrition within Paraguayan territory. Apart from one major Paraguayan victory at Curupayty, most battles were won by the Alliance, who, in spite of overwhelming superiority, never managed to land a decisive blow — owing to poor leadership and decision-making. The final phase? Nothing more than guerrilla warfare, which began when the Brazilians seized Asunción, Paraguay’s capital, and ended with Lopez’s death.

The fact that the war lasted so long and claimed so many lives can be pinned to the Paraguayans’ inability to see reality and accept defeat. Leaders like Comandante Robles preferred to rip their dressings from wounds and die as heroes than to give up the fight, according to Captain Richard Burton’s 1870 book, Letters From the Battle-fields of Paraguay. Paraguayan valor seemingly knew no bounds. Poorly armed, prepubescent Paraguayan boy soldiers were regularly slaughtered by adult Brazilian troops. The Brazilian soldiers loathed having to kill the youths, but their commanders knew that the only way to win the war was to destroy the Paraguayan army. “Theirs was a psychology of extremes,” says Whigham, “and they couldn’t stomach or even fathom any halfway choice or measure.”

It’s easy to assume that the war was caused by a megalomaniac’s foolhardy decisions. But there were bigger political factors at play. Argentina and Brazil were both vying for Great Power status, writes Pelham Horton Box in The Origins of the Paraguayan War, and Paraguay was merely “the detonating point of the explosion.” The main factors? Political differences between the three protagonists, the arbitrary nature of the borders at the time and a lack of sensible diplomacy on all sides.

Paraguay lost large swathes of territory to both Brazil and Argentina, but perhaps even more damaging was the mental scarring it caused, and still causes, to the national psyche. It also established the Brazilian military as a major opponent to Brazil’s monarchy, ultimately resulting in the overthrow of Pedro II in 1889. And in Argentina it put to bed the simmering conflict between Buenos Aires and the provinces, solidifying power in the capital once and for all.

“I see a lot of foolishness, fault, bravery and good spirit on all sides,” sighs Whigham. “It’s just a huge tragedy.”