Mexican War of Independence
Iturbide's assignment to the Oaxaca expedition coincided with a successful military coup in Spain against the monarchy of Ferdinand VII. The coup leaders, part of an expeditionary force assembled to suppress the independence movements in the Americas, had turned against the monarchy. They compelled the reluctant Ferdinand to reinstate the liberal Spanish Constitution of 1812 that created a constitutional monarchy. When news of the liberal charter reached Mexico, Iturbide perceived it both as a threat to the status quo and a catalyst to rouse the criollos to gain control of Mexico. Independence was achieved when conservative Royalist forces in the colonies chose to rise up against the liberal regime in Spain; it was an about-face compared to their previous opposition to the peasant insurgency. After an initial clash with Guerrero's forces, Iturbide assumed command of the royal army. At Iguala, he allied his formerly royalist force with Guerrero’s radical insurgents to discuss the renewed struggle for independence.
Republic of the Rio Grande
After a decade of strife, Mexico won its independence from the Kingdom of Spain in 1821. After a failed attempt at a monarchy, Mexico adopted a new constitution, the 1824 Constitution. This new constitution established los "Estados Unidos Mexicanos", or "the United Mexican States," as a federal republic. During the war for independence, many rebels were driven to Coahuila and Nuevo León, where this revolutionary mentality won the hearts and minds of the people.