Antonio López de Santa Anna
War of Independence, 1810–1821

Santa Anna's early military career during the Mexican War of Independence, which entailed fighting the insurgency before switching sides against the crown, presaged his many shifts in allegiance during his later political career. In June 1810, the 16-year-old Santa Anna joined the Fijo de Veracruz infantry regiment. In September of that year, secular cleric Miguel Hidalgo y Costilla sparked a spontaneous mass uprising in the Bajío, Mexico's rich agricultural area. Although some creole elites had chafed as their upward mobility had been thwarted by the Bourbon Reforms, the Hidalgo Revolt saw most creoles favoring continued crown rule. In particular, Santa Anna's family "saw themselves as aligned to the peninsular elite, whom they served, and were in turn recognized as belonging".

Initially Santa Anna, like most creole military officers, fought for the crown against the mixed-raced insurgents for independence; his commanding officer was Colonel José Joaquín de Arredondo. In 1811 he was wounded in the left hand by an arrow while fighting in the town of Amoladeras, in the intendancy (administrative district) of San Luis Potosí. In 1813 he served in Texas against the Gutiérrez–Magee Expedition and at the Battle of Medina, in which he was cited for bravery. Santa Anna was promoted quickly; he became a second lieutenant in February 1812 and first lieutenant before the end of that year. During the initial rebellion, the young officer witnessed Arredondo's fierce counterinsurgency policy of mass executions. The early fighting against the rebels gave way to guerrilla warfare and a military stalemate.

When royalist officer Agustín de Iturbide switched sides in 1821 and allied with insurgent Vicente Guerrero, fighting for independence under the Plan of Iguala, Santa Anna also joined the fight for independence. Political developments in Spain, where liberals had ousted King Ferdinand VII and began implementing the Spanish liberal constitution of 1812, made many elites in Mexico reconsider their options.
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