During his three-year rule, Barrientos and the army suppressed leftist opposition to his regime, including a guerrilla group led by Che Guevara in 1967.

In 1960, for example, a live parachute jump demonstration by Bolivian Air Force soldiers ended in disaster when their equipment failed and 3 of the 15 parachutists fell to their death before a large crowd assembled to view the event.

Barrientos, as Air Force commander, decided to put on a demonstration of his own, and jumped from an airplane himself using one of the parachutes that had failed to open during the earlier debacle.

By the early 1960s, while the ruling MNR party had begun to fall apart due to personal and policy differences between its leading members, Barrientos' stock was clearly on the rise.

In addition, President Paz Estenssoro (elected to a second term in 1960) was leaning more heavily on military support to restore order to various parts of the country where rival pro-MNR militias had turned against each other, often on behalf of specific MNR leaders.

Traditionally, attempts such as these (known as "prorroguismo") have been strongly condemned by the Bolivian political elites, many of whose members may have been waiting for their turn to occupy the Presidential palace for years.

[11] Accepting more military aid and acquiescing to the training of special forces designed to combat possible communist-inspired insurgencies (under the aegis of the Alliance for Progress) made Barrientos particularly popular with Washington.

Barrientos was very concerned with Guevara's alleged popularity among the miners in the southwestern part of the country, and clamped down in the area with some very heavy-handed measures (such as the San Juan massacre).

While the army was fighting the guerrillas, the miners of Siglo XX (a state-owned Bolivian mining town) declared themselves in support of the insurgency, prompting the president to send troops to regain control.

Further, a major scandal erupted in 1968 when Barrientos' trusted friend and Minister of Interior, Antonio Arguedas, disappeared with the captured diary of Che Guevara, which soon surfaced in, of all places, Havana.

However, on 27 April 1969, a Hiller OH-23 helicopter of the Bolivian Air Force[16] (nicknamed Holofernes[17]) that was carrying him struck telephone cables near Arque, killing Barrientos, his aide-de-camp and the pilot.