The Mexican Revolution was the first great popular upheaval of the twentieth century, beginning modestly as an attempt to reform an oligarchic state, but building into a complex and violent struggle. Adolfo Gilly has written the definitive study of a critical stage in Mexico's history, spanning the years between the first peasant uprising against the dictatorship of Porfirio Diaz and Alvaro Obregon's inauguration as president in 1920, the event that marked the end of the revolution.