The war dragged on, becoming a slow process of attrition. The Paraguayan army suffered devastating defeats at Tuyutí (1866) and Curupayty (1866). By 1868, allied forces, bolstered by Brazilian imperial troops, were pushing deep into Paraguayan territory. The fall of Humaitá in July 1868—a fortress once thought impregnable—marked the beginning of Paraguay’s collapse.
Still, López refused to surrender. He withdrew northward, rallying remnants of his forces, reorganizing them, and preparing to make a last stand. It was during this desperate phase that the Battle of Estero Olastí unfolded.
The Road to Estero Olastí
By mid-1869, López had retreated into the Paraguayan hinterlands, conducting guerrilla-style operations while attempting to reorganize what remained of his army. Estero Olastí, a swampy area located not far from Piribebuy and Caacupé, became a strategic point. It offered natural defenses—marshes, forests, and rivers that could slow the advance of numerically superior enemy troops.
The Paraguayan commander at Estero Olastí was General Bernardino Caballero, who would later become Paraguay’s president. Under him were about 5,000 men—mostly exhausted veterans, teenagers, and even elderly conscripts. Many lacked shoes, uniforms, and adequate weapons, but they carried a fierce determination to resist.
The Triple Alliance forces—principally Brazilians with Argentine support—marched toward Estero Olastí under the command of General Câmara. Their numbers, estimated at around 20,000, vastly outmatched the Paraguayans. Yet the marshy terrain meant that victory was not guaranteed. shutdown123