Calleja is regarded by some historians as one of the greatest military commanders that have ever fought in Mexico, because of his astute yet sometimes barbaric methods. With the Grito de Dolores of Miguel Hidalgo on September 16, 1810, supporters of independence rose in many places in New Spain. Within a month many large cities in the central part of the country fell to the rebels — Celaya (September 21), Guanajuato (September 28), Zacatecas (October 7), Valladolid (October 17), and Guadalajara (November 11) among them.