Soon after being named parish priest in the small town of Dolores, Hidalgo began to promote the establishment of various small manufacturing concerns. He realized the need for diversification of industrial activities in an area that had the mines of Guanajuato as its major business. At the same time, during his seven years at Dolores, Hidalgo promoted discussion groups at his house, where Indians, mestizos, criollos, and peninsulares were welcomed. The themes of these discussions were current events, to which Hidalgo added his own input of social and economic concerns. The independence movement was born out of these informal discussions and was directed against Spanish domination of political and economic life in New Spain. December 8, 1810, was set for the beginning of the uprising.

The plans were disclosed to the central government, and the conspirators were alerted that orders had been sent for their arrest. Pressed by this new development, on September 16, 1810, Hidalgo decided to strike out for independence without delay (this date is celebrated as Mexico's independence day). The church bells summoned the people, and Hidalgo asked them to join him against the Spanish government and the peninsulares in the famous Grito de Dolores (Cry of Dolores): "Long live Our Lady of Guadalupe! Death to bad government! Death to the gachupines !" The crowd responded enthusiastically, and soon an angry mob was marching toward the regional capital of Guanajuato. The miners of Guanajuato joined with the native workers of Dolores in the massacre of all peninsulares who resisted them, including the local intendente .

From Guanajuato, the independence forces marched on to Mexico City after having captured Zacatecas, San Luis Potosí, and Valladolid. On October 30, 1810, they encountered resistance at Monte de las Cruces and, despite a rebel victory, lost momentum and did not take Mexico City. After a few more victories, the revolutionary forces moved north toward Texas. In March of the following year, the insurgents were ambushed and taken prisoner in Monclova (in the present-day state of Coahuila). Hidalgo was tried as a priest by the Holy Office of the Inquisition and found guilty of heresy and treason. He was later condemned to death. On July 31, 1811, Hidalgo was executed by firing squad. His body was mutilated, and his head was displayed in Guanajuato as a warning to other would- be insurgents.

After the death of Hidalgo, José María Morelos Pavón assumed the leadership of the revolutionary movement. Morelos took charge of the political and military aspects of the insurrection and further planned a strategic move to encircle Mexico City and to cut communications to the coastal areas. In June 1813, Morelos convoked a national congress of representatives from all of the provinces, which met at Chilpancingo in the present-day state of Guerrero to discuss the future of Mexico as an independent nation. The major points included in the document prepared by the congress were popular sovereignty, universal male suffrage, the adoption of Roman Catholicism as the official religion, abolition of slavery and forced labor, an end to government monopolies, and an end to corporal punishment. Despite initial successes by Morelos's forces, however, the colonial authorities broke the siege of Mexico City after six months, captured positions in the surrounding areas, and finally invaded Chilpancingo. In 1815 Morelos was captured and met the same fate as Hidalgo.

From 1815 to 1821, most of the fighting by those seeking independence from Spain was done by isolated guerrilla bands. Out of these bands rose two men, Guadalupe Victoria (whose real name was Manuel Félix Fernández) in Puebla and Vicente Guerrero in Oaxaca, both of whom were able to command allegiance and respect from their followers. The Spanish viceroy, however, felt the situation was under control and issued a general pardon to every rebel who would lay down his arms.

After ten years of civil war and the death of two of its founders, by early 1820 the independence movement was stalemated and close to collapse. The rebels faced stiff Spanish military resistance and the apathy of many of the most influential criollos. The violent excesses and populist zeal of Hidalgo's and Morelos's irregular armies had reinforced many criollos' fears of race and class warfare, ensuring their grudging acquiescence to conservative Spanish rule until a less bloody path to independence could be found. It was at this juncture that the machinations of a conservative military caudillo coinciding with a successful liberal rebellion in Spain, made possible a radical realignment of the proindependence forces.

In what was supposed to be the final government campaign against the insurgents, in December 1820, Viceroy Juan Ruiz de Apodaca sent a force led by a royalist criollo officer, Augustín de Iturbide, to defeat Guerrero's army in Oaxaca. Iturbide, a native of Valladolid, had gained renown for the zeal with which he persecuted Hidalgo's and Morelos's rebels during the early independence struggle. A favorite of the Mexican church hierarchy, Iturbide was the personification of conservative criollo values, devoutly religious, and committed to the defense of property rights and social privileges; he was also disgruntled at his lack of promotion and wealth.

Iturbide's assignment to the Oaxaca expedition coincided with a successful military coup in Spain against the new monarchy of Ferdinand VII. The coup leaders, who had been assembled as an expeditionary force to suppress the American independence movements, compelled a reluctant Ferdinand to sign the liberal Spanish constitution of 1812. When news of the liberal charter reached Mexico, Iturbide saw in it both a threat to the status quo and an opportunity for the criollos to gain control of Mexico. Ironically, independence was finally achieved when conservative forces in the colonies chose to rise up against a temporarily liberal regime in the mother country. After an initial clash with Guerrero's forces, Iturbide switched allegiances and invited the rebel leader to meet and discuss principles of a renewed independence struggle.

While stationed in the town of Iguala, Iturbide proclaimed three principles, or "guarantees," for Mexican independence from Spain: Mexico would be an independent monarchy governed by a transplanted King Ferdinand or some other conservative European prince, criollos and peninsulares would henceforth enjoy equal rights and privileges, and the Roman Catholic Church would retain its privileges and religious monopoly. After convincing his troops to accept the principles, which were promulgated on February 24, 1821, as the Plan of Iguala, Iturbide persuaded Guerrero to join his forces in support of the new conservative manifestation of the independence movement. A new army, the Army of the Three Guarantees, was then placed under Iturbide's command to enforce the Plan of Iguala. The plan was so broadly based that it pleased both patriots and loyalists. The goal of independence and the protection of Roman Catholicism brought together all factions.

Iturbide's army was joined by rebel forces from all over Mexico. When the rebels' victory became certain, the viceroy resigned. On September 27, 1821, representatives of the Spanish crown and Iturbide signed the Treaty of Córdoba, which recognized Mexican independence under the terms of the Plan of Iguala. Iturbide, a former royalist who had become the paladin for Mexican independence, included a special clause in the treaty that left open the possibility for a criollo monarch to be appointed by a Mexican congress if no suitable member of the European royalty would accept the Mexican crown.