Mexican War of Independence the Congress of Chilpancingo, which gave the insurgency its own legal framework. After the defeat of Morelos, the movement survived as a guerrilla war under the leadership of Vicente Guerrero. By 1820, the few rebel groups survived most notably in the Sierra Madre del Sur and Veracruz. The reinstatement of the liberal Constitution of Cadiz in 1820 caused a change of mind among the elite groups who had supported Spanish rule. Monarchist Creoles affected by the constitution decided to support the independence of New Spain; they sought an alliance with the former insurgent resistance. Agustín de Iturbide led the military
Antonio López de Santa Anna enough to send him to school. In June 1810, the 16-year-old Santa Anna joined the Fijo de Veracruz infantry regiment as a cadet against the wishes of his parents, who wanted him to pursue a career in commerce. In September 1810, secular cleric Miguel Hidalgo y Costilla rebelled against Spanish rule, sparking a spontaneous mass movement in Mexico's rich agricultural area, the Bajío. The Mexican War of Independence was to last until 1821, and Santa Anna, like most creole military men, fought for the crown against the mixed-raced insurgents for independence. Santa Anna's commanding officer was José Joaquín de Arredondo,