The Battle of Boquern was a battle fought from September 7-29, 1932, between the Bolivian and Paraguayan armies in and around the stronghold of Boquern. It was the first major battle of the Chaco War. The outpost (fortn) of Boquern, among others, had been occupied by Bolivian troops since late July 1932 following instructions of president Daniel Salamanca, which led to the escalation of what began as a border conflict into a full-scale war.

The assault on Boquern was the first move of the Paraguayan offensive that was aimed to defeat the Bolivian army and capture territory before Bolivia had fully mobilized its army and resources. Paraguayan Lt. Col. Jos Flix Estigarribia led the attack. The use of mortars, an unknown weapon for the Bolivian troops until then, would give the Paraguayans a decisive advantage during the siege.The first Paraguayan assault on Boquern was repulsed. Both sides suffered from the lack of potable water--the Paraguayans had to get it from Isla Po (50 km or 30 mi to the east), and although the Bolivians had wells inside their compound, they were under heavy Paraguayan fire and were eventually contaminated by the bodies of fallen soldiers. Bolivian aircraft tried with little success to resupply their troops by dropping ammunition, food and medicine--the only supplies the Bolivians managed to get from the air drops were 916 cartridges, a sack of bread and 110 pounds of dried meat. On September 12 a 3,500-man Bolivian relief column coming from the southwest was driven back near the outpost of Yucra. As the siege progressed the Paraguayans began to suffer from a shortage of water from Isla Po due to over-extraction from the wells. In the face of these problems Estigarribia ordered an all-or-nothing attack on the stronghold on September 26. Three days later the remaining Bolivian defenders, consisting of 240 mostly wounded men, surrendered.

The Chaco War (Spanish: Guerra del Chaco, Guarani: Cháko Ñorairõ) was fought from 1932 to 1935 between Bolivia and Paraguay over control of the northern part of the Gran Chaco region (known in Spanish as Chaco Boreal) of South America, which was thought to be rich in oil. The war is also referred to as La Guerra de la Sed (Spanish for "The War of Thirst") in literary circles since it was fought in the semi-arid Chaco. The bloodiest interstate military conflict fought in South America in the 20th century, it was fought between two of its poorest countries, both of which had lost territory to neighbors in 19th-century wars.

During the war, both landlocked countries faced difficulties shipping arms and supplies through neighboring countries. Bolivia, in particular, faced external trade problems and with poor internal communications. Although Bolivia had lucrative mining income and a larger and better-equipped army, a series of factors turned the tide against it, and Paraguay controlled most of the disputed zone when the war had ended.

The peace treaties ultimately granted two thirds of the disputed territories to Paraguay.