3. The Paraguayan War (1864-1870)
The Paraguayan War, or War of the Triple Alliance, was a catastrophic conflict that pitted Paraguay against Brazil, Argentina, and Uruguay. In this brutal struggle, Paraguay lost a staggering portion of its population—some estimates say up to 70%. The defeat devastated the country and dramatically realigned South American geopolitics, empowering neighboring states and shifting the regional balance of power for decades.
