September 27
Mexican Army Enters Mexico City, Securing Independence
The triumphant entry of the Army of the Three Guarantees into Mexico City on September 27, 1821, brought an end to three centuries of Spanish colonial rule after a prolonged war of independence.
Summary
After more than a decade of warfare that began with Miguel Hidalgo's 1810 Grito de Dolores, Mexico's independence struggle continued under leaders like José María Morelos and later Vicente Guerrero. In 1821, royalist officer Agustín de Iturbide allied with insurgents under the Plan of Iguala, promising independence, Catholicism, and equality. The Spanish viceroy signed the Treaty of Córdoba in August, recognizing Mexican sovereignty. On September 27, Iturbide's Army of the Three Guarantees triumphantly entered Mexico City. The following day, independence was formally proclaimed, ending Spanish colonial rule after three centuries.
Context
Napoleon’s 1808 invasion of Spain and the forced abdication of King Charles IV created a crisis of legitimacy across the Spanish Empire. In New Spain, American-born elites known as criollos sought greater local autonomy while remaining loyal to the absent Bourbon monarchy, a stance reinforced by the liberal Spanish Constitution of 1812 drafted in Cádiz. These political tensions intersected with deep social divisions over race, class, and land that had long simmered in the viceroyalty.
What Happened
By early 1821, royalist officer Agustín de Iturbide had negotiated an alliance with insurgent leader Vicente Guerrero under the Plan of Iguala, which called for Mexican independence, the preservation of Catholicism, and legal equality among racial groups. The two forces combined into the Army of the Three Guarantees and advanced rapidly as royalist resistance collapsed. Newly arrived Spanish viceroy Juan O’Donojú met Iturbide and signed the Treaty of Córdoba on August 24, 1821, formally recognizing Mexican sovereignty.
Aftermath
On September 28, 1821, independence was officially proclaimed in Mexico City. Iturbide was soon crowned emperor of the First Mexican Empire, though that monarchy proved short-lived and gave way to a federal republic by 1823. Spain withheld diplomatic recognition until the Santa María–Calatrava Treaty of 1836.
Legacy
Mexico’s independence removed the largest remaining Spanish possession in the Americas and set a precedent that encouraged independence movements elsewhere in Latin America. The new nation’s subsequent political instability and territorial losses in the nineteenth century reshaped the balance of power across North America.
Why It Matters
Mexico's independence created the first major republic in the Americas after the United States and Haiti, inspiring other Latin American independence movements. It established a new nation whose political instability and territorial losses in the 19th century reshaped North American geopolitics.
Related Questions
What triggered the Mexican War of Independence?
Napoleon’s invasion of Spain in 1808 undermined the legitimacy of Spanish rule and inspired criollo elites to seek greater autonomy.
Who were the main leaders of the independence movement?
Miguel Hidalgo began the armed revolt in 1810; José María Morelos directed the next phase; Vicente Guerrero sustained the insurgency until allying with Agustín de Iturbide in 1821.
What was the Plan of Iguala?
Iturbide’s February 1821 proclamation that united royalists and insurgents around the goals of independence, Catholicism, and racial equality.
When did Spain officially recognize Mexican independence?
Spain withheld recognition until the Santa María–Calatrava Treaty of 1836, fifteen years after the 1821 events in Mexico City.
What immediate political form did independent Mexico take?
The country was organized as the First Mexican Empire under Agustín de Iturbide before becoming a federal republic in 1823.
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Sources
- September 27 - Wikipedia, Wikimedia Foundation. Accessed 2026-07-05.
- Mexican War of Independence - Wikipedia, Wikimedia Foundation. Accessed 2026-07-05.