Quintanilla saw action in the initial stages of the Chaco War (1932–1935) and managed to ascend the echelon of the Bolivian armed forces until he became commander of the army during the administration of Germán Busch.

Though Quintanilla had ambitions of exercising a longer government, pressure from both the left and right wings of the political spectrum forced him to call general elections on 10 March 1940.

Despite his pledge to "continue the [...] social and economic policy" of Busch, Quintanilla's short mandate was spent dismantling the socialist laws of his predecessors and ensuring that the conservative traditional parties of the pre-Chaco war era returned to power.

Before this could go into effect, on 9 September, Quintanilla suddenly found himself facing the first Paraguayan offensive led by lieutenant colonel José Félix Estigarribia, an officer of lower rank but superior professional training and experience.

Consequently, the Army ignores the authority of the President of the Republic and continues to recognize and will support General Osorio in his capacity as Chief of Staff in the Campaign".

[5] Whatever the case, a lack of support from other officers and the intervention of former president Ismael Montes forced Toro and Quintanilla to retract their attempted insubordination.

It would not be until January 1935, after the overthrow of Salamanca, that Quintanilla returned to the front, participating in the Battle of Villamontes now as the General Commander of the Central Sector, in the final phase of the Chaco War.

As a result of Bolivia's loss in the Chaco War, the old political order of Salamanca and his successor José Luis Tejada Sorzano were quickly painted by military officers like Quintanilla as responsible for the country's failure.

However, Quintanilla, like many of his fellow conservative senior officers, was weary of the reckless reformist wave unleashed by the Military Socialist David Toro and Germán Busch regimes which followed.

Busch, despite his experience of governing the army, was politically naive and allowed Quintanilla free rein to oust the younger liberal officers from their position of power.

Seeing that the ailing president was unlikely to recover, the general then travelled with full speed back to the center of La Paz where he staged a military occupation of the Palacio Quemado, the government palace.

As such, the military also argued that Baldivieso had renounced his constitutional right to succession by engaging in the self-coup which dissolved the assembly and made Busch dictator months prior.

[8] Months later on 4 December, by simple decree Quintanilla amended article 90 of the 1938 Constitution, outright abolishing the vice presidency claiming that the office was "not justified either by public needs or by the political tradition of the country".

[10] In the immediate aftermath of Busch's suicide, Quintanilla was faced with the task of stabilizing the country while also dispelling accusations that he was enacting a coup and that the president had been assassinated.

In order to reinforce the version of Busch's suicide, the government of Quintanilla issued a statement on 24 August which "leaves on record with full evidence that the death of the president is due to an absolutely voluntary act by determination made under the weight of his deep patriotic anguish".

[11] Despite swearing that his government would "continue the directives and orientations of the social and economic policy of Colonel Busch's,"[10] his main acts in his brief capacity as president were to begin the process of returning the country to the pre-war oligarchic status quo, complete with its faults and relative stability.

[9] His decision to issue fiduciary currency without legal support caused an inflation in the prices of basic necessities, worsening the country's dire economic situation.

For his actions in moving the country away from the era of military socialism, two senators suggested he be promoted to none other than the prestigious rank of Marshal of Bolivia, a title not held since Andrés de Santa Cruz and Otto Philipp Braun.

The proposal failed and became the subject of mockery and popular epigrams deriding the idea with Quintanilla himself being awarded the derogatory nickname of "El Loco Mariscal" (The Crazy Marshal) as a result.

[16] Following this, Quintanilla declared that "In the protection of social tranquillity, threatened in recent days and in my duty as a leader, I have accepted with feeling, but without hesitation the departure of General Bilbao Rioja".

Instead of being allowed to return to his post, Bernardino Bilbao was given little choice but to accept an appointment as military attaché in London, travelling there directly from Chile in a disguised exile.

[17] The failed revolt was followed by an anti-coup demonstration in the plaza which was joined by supporters of the Concordance, employees of the Foreign Ministry, and left-wing figures such as Hernán Siles Zuazo and Rafael Otazo.