He served as Secretary of War in the cabinets of Presidents Plutarco Elías Calles, Emilio Portes Gil, and Pascual Ortiz Rubio, making him one of the longest-serving cabinet-level officials in Mexican history.

He accomplished this "through a process of cultural reeducation that replaced an entrenched tradition of militarism with one emphasizing such values as discipline, duty, honor, and loyalty to the civilian government.

In 1910, his father sold his possessions and gave the money to his eldest son, advising him, "go to Durango with your mother and siblings, work for Mr. Calderón [a local store-owner], learn the business, get to know the town, and when you feel able, open your own store.

"[2] His father left for Torreón in November of that year, and although Amaro never saw him again, he read about his exploits with the revolutionary army of Colonel Luis Moya.

As part of the army of Colonel Gertrudis G. Sánchez, whose forces Arrieta's had joined, Amaro fought against the Zapatistas in Morelos, engaging them at least nineteen times.

The split finally came in 1915, when Amaro advanced the troops under his command on the Villista División del Norte, leaving Sánchez in Michoacán.

Following the battle, Obregón named him Comandante militar ("military commander") of the 5th Division of the Army of the Northwest, and he was charged of ridding Michoacán of villista influence.

On September 3, 1921, while chief of operations of the third military zone, Amaro wed Elisa Izaguirre, originally of Morelia, Michoacán.

When in 1922 political unrest threatened to destabilize Coahuila, Amaro positioned his troops to block the occupation of the state legislature and to protect the governor's palace.

Today, most historians attribute Villa's death to a well planned conspiracy, most likely initiated by then Minister of War Plutarco Elías Calles, who ordered Amaro to give support to the assassins.

Calles gave Amaro full support in continuing the latter's plan to reform the Mexican armed forces along anti-clerical and populist lines: I have fought without rest [...] against clericalism, large landowners, the militarism of the ex-Federals, the Spanish, and in general all those that do not contribute to the enrichment of our beloved homeland and the betterment of the working

[5] In 1923, Amaro's chief of staff José Álvarez learned of the plot between generals Enrique Estrada, Guadalupe Sánchez, and Fortunato Maycotte to overthrow Obregón.

The conspirators drafted Adolfo de la Huerta, then-Minister of Finance, to run for president against Plutarco Elias Calles, Obregón's chosen successor.

Facing a rebellion with armies in the North, South, and East, Obregón relied on loyal generals such as Amaro to block rebel access to resources and the northern border and to put down the insurrection.

While undersecretary, Amaro initiated a series of legal reforms to purge the armed forces of "the germ of immorality and corruption.

These reforms were an effort to end the practice of opportunistic and haphazard promotions which had inflated the number of generals in Mexico's officer corps during the Revolution.

The first section sought to redefine the relationship between generals and the soldiers under them, demanding that all personnel be loyal to the nation and the constitution and take their orders from the President or his designees.

Upon his appointment to the Secretariat, Amaro moved to Rancho de la Hormiga, a 40,468 square meter (ten acre) ranch that later became the presidential palace Los Pinos.

While Revista was aimed at the officer corps, Amaro founded El Soldado, which emphasized the same themes, as a supplement for enlisted men.

He was slow to advance the progress of the Mexican Air Force, which had only three squadrons of obsolete aircraft during Amaro's tenure as Minister of War.

When President Obregón was assassinated by pro-clergy forces sixteen days after his 1928 re-election, many generals and other important figures in Mexican politics urged Amaro to run for the office.

During his three-month convalescence, which left him with a glass eye, Calles assumed the Secretariat, in which capacity he put down the Escobar rebellion against Emilio Portes Gil, who had been appointed interim president in the wake of Obregon's assassination.

The reforms, his involvement in suppressing leftists and the now-confirmed suspicion of his role in Pancho Villa's assassination, made Amaro very unpopular in some circles and a target of vicious, false rumors.

However, contemporary news reports in the Evening Courier, Camden, NJ and New York Times show the story of the "fateful telegram" to be a fabrication.

[9] [10] Another example is the story that Amaro shot and killed a groom whom disobeyed his order to walk his polo pony and instead rode it to the stables, which the U.S.

[11] However, there is good reason to believe that Ambassabor James R. Sheffield loathed the Mexican Revolutionary leaders and would have passed on any rumor to discredit them regardless of its veracity.

"[12] Amaro sought to create a Superior War College along the lines of France's École Supérieure de Guerre to train an elite group of officers.

On October 1942, during World War II, Amaro was reintegrated into the army, where he was responsible for defending the region of the Isthmus of Tehuantepec from Axis aggressions.