Bolivia and Paraguay are both landlocked neighbors in South America. Neither have had the luxury of strong economies.

Between 1932 and 1935, the two countries fought the bloodiest conflict on the continent in the 20th century.

At dispute, was a region known as “Gran Chaco” which was incorrectly believed to contain substantial oil deposits. Control of the region also meant use of the Paraguay River which flows to the Atlantic and acts as a gateway similar to the Mississippi in the United States.

Bolivia had lost its access to the sea during a conflict with Chile at the end of the 19th century. This meant that the country was forced to rely on permission from neighboring countries to allow the passage of arms transfers.

Paraguay also lost territory at the end of the 19th century in a decidedly uneven conflict against Brazil, Argentina and Uruguay. An astonishing 300,000 soldiers and civilians were killed during the Paraguayan War.

Paraguayan soldiers manning a Vickers machine gun.

Despite international arbitration, on September 7th, 1932, Paraguayan forces laid siege to Fortín Boquerón on Pitiantutá Lake within the disputed region for 22 days.

A series of confrontations and incivilities had been leading up to the event for years, and conflicts in the region between the two nations date at least to 1885 when a Bolivian founded a fort known as Puerto Pacheco on the upper Paraguay river at a port. His fort had been placed on territory recognized by his own government as Paraguayan territory, and resulted in the forced eviction by the government of Paraguay. However, in first quarter of the 20th century, continued incursions and settlements by Bolivians in the region continued.

Despite a population approximately half that of Bolivia, Paraguay nevertheless gained the upper hand during the conflict by using guerrilla tactics compared to Bolivia’s more conventional tactics.

Additionally, just as the United States forces would later make use of the language of the local Navajo peoples in the Pacific during World War II, the Paraguayan armed forces communicated over radio in Guaraní, which was not understood by the average Bolivian soldier.

Paraguayan forces were better able to mobilize, equip, and deploy than Bolivian forces.

By the end of the war, an estimated 85,000 to 130,000 had been killed during the conflict. At the time of the ceasefire in 1935, Paraguay controlled a majority of the region, and gained three quarters of the approximately 20,000 square miles in dispute according to the truce in 1938.

Based on the definitions of the treaty defining the disputed area, approximately two Paraguayans and three Bolivians had been killed for every square mile in the region in dispute.

Not until April 28, 2009, was a formal treaty between the two nations signed, clearly defining the boundaries between the countries in Gran Chaco.