The Spanish Revolution of 1820 was a military mutiny that compelled Ferdinand VII to restore the Cádiz Constitution, reopening a constitutional crisis across Spain’s American colonies. In Mexico, the renewed constitutional settlement helped persuade elites who had resisted popular political participation to pursue independence on terms designed to protect their own privileges.

Crisis in the Spanish Empire

The revolution arose from the upheaval caused by Napoleon’s invasion of Spain. After the Spanish state collapsed into crisis, colonial authorities and residents disputed whether to recognize the Junta Central, and many Latin Americans formed their own juntas. The possibility of independence grew out of this uncertainty. In 1809, La Paz declared independence, but Spanish troops sent from Peru quickly crushed the movement.

Mexico’s elites had already been shaped by the Hidalgo Revolt of 1810. After Father Miguel Hidalgo’s army sacked Guanajuato and killed the senior colonial official, violence against white residents helped unite elites against the prospect of popular political participation. The episode appeared less like an independence movement to those elites than a class or ethnic conflict. Their opposition to the Cádiz Constitution was therefore rooted not only in loyalty to Spain: they also feared that its opening to popular participation would threaten local power.

The Mutiny and the Restored Constitution

In 1815, as Napoleon’s European empire collapsed, Ferdinand VII returned to power and the Cádiz Constitution was abrogated. The Spanish Crown began trying to reclaim its American colonies, but Mexico remained loyal. The turning point came in 1820, when a Spanish army assembled at Cádiz to sail to the Americas mutinied against Ferdinand. Army units across Spain joined the revolt, forcing the king to restore the constitution and recall the Cortes.

The recalled Cortes was more radical than the assembly that had written the original constitution. It proposed abolishing all forms of labor coercion and challenged special privileges, including the military’s right to try its own members for crimes. For Mexican elites, the prospect of having this program imposed was more threatening than separation from Spain. The revolution thus helped reverse their earlier position: an independent Mexico became a means of avoiding reforms that might unsettle the existing order.

Independence on Elite Terms

Agustín de Iturbide, a former officer in the Spanish army, led the independence movement. On February 24, 1821, he published the Plan de Iguala, which proposed an independent Mexico under a constitutional monarchy headed by a Mexican emperor. Its terms removed the provisions of the Cádiz Constitution that Mexican elites considered dangerous to their status and privileges. The plan won immediate support, and Spain soon recognized that it could not prevent Mexican independence.

Iturbide’s course also exposed the gap between constitutional language and the concentration of power. With military backing and a political vacuum at hand, he had himself declared emperor. Simón Bolívar described the basis of his authority as “by the grace of God and of bayonets.” By October 1822, Iturbide had dismissed the constitutionally sanctioned congress and replaced it with a junta of his choosing. His rule did not last long, but the account presents this sequence—independence followed by personal dictatorship—as a pattern that would recur in nineteenth-century Mexico.

A Revolution with Uneven Consequences

The Spanish Revolution of 1820 was not itself Mexico’s declaration of independence. Its importance lay in forcing the restoration of a constitution whose proposals made continued loyalty less attractive to Mexican elites. The ensuing independence movement retained monarchy and elite privilege rather than embracing the Cádiz Constitution’s broader challenge to them.

The episode illustrates how political upheaval can open a path to institutional change without determining who will benefit from it. In the broader account, inclusive institutions emerge through conflict, but outcomes remain contingent; mobilization and constitutional rupture do not guarantee pluralism. In Mexico, the immediate consequence of the restored constitutional program was not its acceptance but elite-led secession, followed by Iturbide’s seizure of power and the dismissal of congress.