Originally rather apolitical, he was chosen (among others) to lead the reconstituted Armed Forces of Bolivia in the aftermath of the 1952 Revolution that installed in power the reformist Revolutionary Nationalist Movement party, better known as the MNR.

Equally as important in this rebirth was the considerable pressure exerted by the United States to modernize and equip the troops for a decidedly more political role: that of fighting possible Cuba-styled Communist insurgencies.

Uncharismatic but tenacious, Ovando was biding his time, counting on the fact that he would be the logical choice to run for elections once Barrientos' term ended in 1970, perhaps with some electoral "help" from the outgoing administration.

While the popular insurgency was eventually crushed by the US-trained Bolivian military troops under American CIA command, Guevara was captured and executed in October 1967.

This event embarrassed US military School of the Americas (SOA) graduate Barrientos as a US-controlled puppet, and prompted Ovando to distance himself from the president with an eye to the projected 1970 elections.

For these reasons, Ovando decided not to wait for the elections (which no one could guarantee he could win, with the popular Escobar as candidate) and on 26 September 1969, he executed a coup d'état that overthrew Siles.

Ovando's populist stance surprised many conservative members of the Bolivian military and failed to fully satisfy the increasingly more belligerent forces of the Left, especially the workers and students.

In June 1970, a new Marxist guerrilla movement emerged in the lowlands near La Paz, this time constituted mostly by Bolivian university students aligned with the outlawed Ejército de Liberación Nacional (National Liberation Army, or ELN).

Embarrassed by his quick abandonment of the fight, and worn out by 13 grueling months in office, Ovando agreed to leave the presidency in the hands of his friend, General Torres.