Ovando (copresident, May 1965-January 1966, and president, January-August 1966 and 1969-70) annulled the elections scheduled for 1970, dismissed the Congress, and appointed a cabinet that included independent reformist civilians who had opposed the policies of Barrientos. Ovando hoped to gain civilian and military support with a program of "revolutionary nationalism," which he had outlined in the "Revolutionary Mandate of the Armed Forces." Revolutionary nationalism reflected the heritage and rhetoric of the military reformist regimes of the past, as well as the spirit of the 1952 Revolution. It also showed the influence of the Peruvian government of General Juan Velasco Alvarado. Many Bolivian officers believed that the military had to intervene in politics to lead the country toward reform because civilian governments had failed in that undertaking. They were convinced that it was in the main interest of the armed forces to end underdevelopment, which they saw as the cause of insurgency. The military would therefore fight on the internal frontiers against social injustice and economic dependence.

Despite highly popular measures, such as the nationalization of the holdings of the North American-owned Gulf Oil Company, Ovando failed to gain popular support. Popular enthusiasm over the nationalization was short lived. Disagreement over compensation, a boycott of Bolivian crude oil on the international market, and a general downturn in the economy became divisive factors. Even though Ovando legalized the COB and withdrew troops from the mining camps, lasting worker support for the regime was not ensured. Frustrated expectations, broken promises, and the massacre of miners by the military in Catavi in 1967 had radicalized the workers, who now refused to cooperate with the military government.

While the left became radicalized, the right became weary of Ovando's vacillating statements, which included the suggestion that private property be abolished. Even when Ovando moved right during the last months of his regime, he was unable to enlist the support of the conservative groups in the country because this move only emphasized his weakness.

Ovando's reform program also polarized the military. Reformist officers, concerned about the decline in popular support for the military since the Barrientos regime, shifted their support to the more radical General Juan José Torres González (1970-71), whom Ovando had dismissed as his commander in chief; the right backed General Rogelio Miranda. The chaos surrounding the overthrow of Ovando highlighted the division in the armed forces. Military officers demanded the resignation of Ovando and Miranda after a failed coup attempt by the latter on October 5, 1970. A triumvirate, formed on October 6, failed to consolidate support. On October 7, as the country moved toward civil war after the COB had declared a general strike, General Torres emerged as the compromise candidate and became president of Bolivia.

The main feature of Torres's presidency was a lack of authority. Rather than taking the initiative on policies, Torres primarily reacted to pressure from different groups. His minister of interior, Jorge Gallardo Lozada, labeled the Torres government the "ten months of emergency."

Torres hoped to retain civilian support by moving to the left. He nationalized some United States property, such as the wasteprocessing operation of the Catavi tin mines and the Matilde zinc mine, and he ordered the Peace Corps, a United States program, out of Bolivia. While limiting United States influence in Bolivia, Torres increased cooperation with the Soviet Union and its allies in the economic and technical sectors.

Because of his lack of a clear strategy and political experience, however, Torres soon succeeded in alienating all sectors of Bolivian society. He found it very difficult to organize groups on the left because they confronted him with demands that he could not meet, such as giving them half of all cabinet seats. The workers, students, and parties of the left wanted a socialist state and saw the Torres government only as a step in that direction. In June 1970, the Torres regime established the Popular Assembly (Asamblea Popular) in an attempt to form an alternative popular government. Consisting mainly of representatives of workers' and peasants' organizations, the Popular Assembly was intended to serve as a base for the radical transformation of society. However, the left remained divided by ideological differences and rivalry for leadership. They could not agree on controversial issues dealing with full worker participation in state and private enterprises, the creation of armed militias, and the establishment of popular tribunals having legal jurisdiction over crimes against the working class. No consensus was achieved, and many delegates, resenting the lack of power to enforce the resolutions and running short of funds, returned home prematurely. The Popular Assembly did, however, succeed in weakening the government by creating a climate in which popular organizations acted independently from the state.

Torres's hope of placating conservative opposition by avoiding radical change did not win him the support of the right, especially of the powerful business community. Conservative groups unified in their opposition because they saw a chance for a political comeback in alliance with rightist officers. The military, in turn, became increasingly polarized because of their discontent with Torres's chaotic leadership. Torres had cut the defense budget to free money for education and allowed civilian interference in strictly military matters. He often premitted military disobedience to go unpunished. The last step of institutional decay was a manifesto written during the last weeks of the Torres regime by a group of junior officers who questioned military authority. It resulted in widespread military support for the coup on August 21, 1971, by Colonel Hugo Banzer Suárez, the former Military Academy commander whom Torres had exiled.

Data as of December 1989