The Battle of Kilometer 7 occurred during the Chaco War

Chaco War

The Chaco War was fought between Bolivia and Paraguay over control of the northern part of the Gran Chaco region of South America, which was incorrectly thought to be rich in oil. It is also referred to as La Guerra de la Sed in literary circles for being fought in the semi-arid Chaco...

 between Bolivia

Bolivia

Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

n forces commanded by Lt Col Bernardino Bilbao Rioja

Bernardino Bilbao Rioja

Bernardino Bilbao Rioja was a Bolivian officer who served during the Chaco War . He pioneered the use of air forces in combat ....

 defending Fort Saavedra and Paraguay

Paraguay

Paraguay , officially the Republic of Paraguay , is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to the east and northeast, and Bolivia to the northwest. Paraguay lies on both banks of the Paraguay River, which runs through the center of the...

an forces under Col José Félix Estigarribia

José Félix Estigarribia

Marshal José Félix Estigarribia Insaurralde was a decorated Paraguayan war hero and President of Paraguay for the Liberal party. Educated as an agronomist, he joined the national Army in 1910 and spent time in Chile and in Saint Cyr's military academy in France for additional training...

, from 7 November 1932 to February 1933, and ended with a Paraguayan retreat to the northeast towards Gondra, later to be the site of the Battle of Campo Jordán

Battle of Campo Jordán

The Battle of Campo Jordán occurred during the Chaco War, with victory going to the Bolivians, who forced the Paraguayans to retreat towards Gondra, on losing Alihuatá and the supply route of the Saavedra-Alihuatá road....

. The Paraguayan iniciative, which had belonged to the Paraguayans since the beginning of the siege of Boquerón

Battle of Boquerón

The Battle of Boquerón was a battle fought from September 7 to 29 in 1932 between the Bolivian and Paraguayan armies in and around the stronghold of Boquerón. It was the first major battle of the Chaco War...

 passed to the Bolivian army until the Second Battle of Nanawa

Second Battle of Nanawa

The Second Battle of Nanawa was a battle fought from July 4 to 9 in 1933 between the Bolivian and Paraguayan armies during the Chaco War. It was one of the bloodiest battles fought in South America in the 20th century, coming to be labeled as the "South American Verdun" by comparison with the...

in July.