Despite the blood-letting in Mexico’s War for Independence, about the only thing that was accomplished in the ten years after Miguel Hidalgo’s Grito de Dolores was the death of hundreds of thousands of people, political anarchy, and economic ruin. Both Royalists and Republicans, exhausted from their efforts and baffled by the confusion in Spain as a result of the Napoleonic Wars and aftermath, began to negotiate with each other. The chief negotiators were Royalists officer Augustín de Iturbide—El Dragón de Hierro (The Iron Dragoon)—and Republican Vicente Guerrero. As the negotiations progressed, Republican Guadalupe Victoria joined the conversation.
On February 24, 1821, these talks produced the Plan de Iguala, which advocated three guarantees: Freedom from Spain, The Roman Catholic Religion, and Union of all the castes of Mexico. The leaders combined their armies into the Army of the Three Guarantees and marched toward Mexico City. The Plan de Iguala, at its root, sought a royal monarchy for Mexico—hopefully a European potentate from the House of Bourbon if not the politically crippled Spanish King Ferdinand VII himself–as long as this new ruler observed the “three guarantees.”
Rebels, criollos, Indians, clergy, Royalists, and Peninsulares alike supported the vaguely worded document but the Spanish government in Mexico City and Madrid both resolutely rejected it.
The last Viceroy of Mexico, Juan de O’Donoju, understood the tides of history, however, and agreed to most of the issues at hand, with the addition that independent Mexico could select its own monarch should no candidate from Europe present himself. Under the Treaty of Córdoba between Mexico and Spain, a five-person regency would hold the reins of power until a new monarch arrived.
On September 27, 1821, The Army of the Three Guarantees marched peacefully into Mexico City to begin the nation’s transition to independence.