Unfortunately he backed the wrong horse. At least, that's what it looked like when Madero was overthrown and assassinated by Victoriano Huerta in February 1913. Huerta declared himself ruler of Mexico, and Obregón joined a coalition government against Huerta. He was well-respected enough after just three years of military experience to be named named commander-in-chief of the rebel army! Excuse me, the "Constitutional Army of the Northwest." Under him, the rebels conquered and then controlled most of Mexico's northwest.
Nice, but insufficient. As long as the Huerta held Mexico City, he would be viewed as the true power in Mexico, and everyone else would be mere rebels. So Álvaro Obregón took Mexico City. It was more exciting than that, with grand military strategies and tactical maneuvers, but by August 1914, Obregón was marching in triumph through the streets of the city. One Venustiano Carranza was installed as the first president of the new republic.
The fighting wasn't quite over. The next year, Obregón led forces against the rebel leaders and . See how quickly the rebels become the establishment? It was during fighting against Villa that Obregón lost his right arm. For the rest of his life, Obregón wore clothing tailored to show that he had lost his arm in battle, a visible sign of his sacrifice to Mexico.
With Villa and Zapata pacified in 1917, Obregón declared his work over. After a brief stint on Carranza's cabinet, he retired to his farm in Sonora. In April 1920, however, in response to Carranza’s increasingly reactionary policies and his attempt to impose a puppet successor, Obregón took a leading role in the uprising that quickly overthrew the president. In December, Obregón was elected president.
He proved to be the first stable president since the Mexican Revolution of 1910. Obregón managed to impose relative peace and prosperity on his nation, after ten years of official and unofficial civil war. He gave official support to organizations of laborers and peasants. Moreover, his government led an era of significant reform in Mexican schooling, and supported a flourishing of the arts. During his presidency, there were two armed insurrections which were quashed. Mexico was (mostly) at peace.
Obregón "retired" in 1924. His chosen successor continued to give him great influence, and Obregón built up his agricultural empire in northern Mexico and established a monopoly on chickpeas. He was re-elected president in 1928, despite another armed revolt which the government handily suppressed. But before he could be sworn in, Alvaro Obregón was assassinated.
Today, his embalmed arm lies in a monument at the site where he was killed.