Humaitá campaign

The Humaitá campaign or the Cuadrilátero campaign was the third, longest and deadliest campaign of the Paraguayan War. The campaign lasted from 16 April 1866 to 5 August 1868. After the initial Paraguayan success in the Mato Grosso campaign and its failure in the Corrientes campaign, the armed forces of the Triple Alliance, Argentina, the Empire of Brazil and Uruguay, invaded the south of Paraguay. At a very short distance, they found the Paraguayan defensive device made up of four fortifications, the so-called "Cuadrilátero", which obstructed the passage to Asunción both by land and by the Paraguay River. A long series of battles cost huge numbers of casualties on both sides, with operations coming to a complete halt after the allied defeat at the Battle of Curupayty. Casualties on both sides were even higher from disease than from battle due to a cholera epidemic which was added to the appalling food and sanitary conditions.

All operations were halted from September 1866 to July 1867, when the allied offensive resumed. By the middle of the following year, however, little progress had been made when the fortifications were overrun by the Brazilian fleet. Faced with this novelty, the Paraguayan forces installed a new defensive line, much closer to Asunción, abandoning the "Cuadrilátero". Ultimately, the campaign resulted in a costly but unqualified success for the Triple Alliance.