The Army of the Three Guarantees was formed by the unified forces of Iturbide and Guerrero to defend the ideals of the Plan of Iguala.

These are the "Three Guarantees" by which the Plan is sometimes known, summarized as "Religion, Independence and Unity" ("Religión, Independencia y Unión").

The document explicitly includes all residents of Mexico's geographic territory among its citizens: the preamble refers to "Americans, under which term are included not only those born in America, but Europeans, Africans and Asians who reside in it," and Article 12 states: "All the inhabitants of the Mexican Empire, without any other distinction besides merit and virtue, are suitable citizens to apply for any employment," or "All the inhabitants of New Spain, without any distinction between Europeans, Africans, nor Indians, are citizens of this Monarchy with option to all employment depending on their merit and virtues," depending on the copy.

The Mexican government, however, insisted upon O'Donojú's acceptance of the Plan as legally establishing the country's independence and sovereignty.

[9][10] Following the fall of Iturbide's empire, the Mexican Congress abrogated both the Plan of Iguala and the Treaty of Córdoba as the basis for the government on 8 April 1823.