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.
Miguel Ramos Arizpe
The insurgency for Mexican independence that began with Father Miguel Hidalgo's 1810 uprising and carried on by Father José María Morelos, and Vicente Guerrero during the 1810s was at a military stalemate with royalist forces. With the 1820 Spanish Constitution, the power of the Roman Catholic Church in Mexico was threatened. Royalist military officer Agustín de Iturbide made an alliance with Guerrero, and under the Plan de Iguala declaring Mexico's independence, which was achieved in 1821. The formation of the new Mexican state initially involved a constituent congress, but Iturbide seized power and declared himself Agustín I, emperor of Mexico. Ramos Arizpe returned to Mexico in 1822, when opposition to Iturbide was coalescing. He was "instrumental in mobilizing the provinces and drafting the Plan of Casa Mata," which called for the overthrow of Iturbide.