The
Chaco War (Spanish:
Guerra del Chaco,
Guarani:
Cháko Ñorairõwas fought from 1932 to 1935. It was between
Bolivia and
Paraguay over control of the northern part of the
Gran Chaco region (known in Spanish as the
Chaco Boreal), which was thought to be rich in
petroleum. The war is also referred to as
La Guerra de la Sed (Spanish for "The War of Thirst"), since it was fought in the
semi-arid Chaco. It was the first South America war in which modern weapons (such as
machine guns,
armoured fighting vehicles and airplanes) were used, and also the bloodiest South America war of the 20th century — around 2% of the Bolivian population and 3% of Paraguayans were killed during the conflict.
During the war, both
landlocked countries faced difficulties moving arms and supplies through neighbouring countries. Despite its income from mining and a larger and better-equipped army, problems with international trade and poor internal communications ultimately turned the tide against Bolivia. The war concluded at the Chaco Peace Conference in
Buenos Aires in July 1938, at which both countries signed a peace treaty awarding three-quarters of the Gran Chaco to Paraguay.
The war cost both nations dearly. Bolivia lost between 56,000 and 65,000 people, 2% of its population, and Paraguay lost about 36,000, or 3% of its population. Paraguay captured 21,000 Bolivian soldiers and 10,000 civilians (1% of the Bolivian population); many of the captured civilians chose to remain in Paraguay after the war. In addition, 10,000 Bolivian troops, many of them ill-trained and ill-equipped conscripts, deserted to Argentina or injured or mutilated themselves to avoid combat. By the end of hostilities, Paraguay had captured 42,000 rifles, 5,000 machine guns and submachine guns, and 25 million rounds of ammunition from Bolivian forces
https://en.wikipedia.org/wiki/Chaco_War