On September 27, 1821, the Trigarant Army entered Mexico City triumphantly. With this fact it is considered the consummation of the independence struggle that began on September 16, 1810, with the Grito de Dolores given by the priest Miguel Hidalgo.
The Trigarante Army entered the capital of the country under the command of Agustín de Iturbide, who since October 1820 began with his plans for independence.
Iturbide had been one of the prominent members of the realistic army. In November 1820, he was appointed general commander of the South and was commissioned to fight Vicente Guerrero, who had become one of the main leaders of the insurgents and independentists.
On January 10, 1821, Iturbide writes to Vicente Guerrero to invite him to surrender for independence on the way. Ten days later, on January 20, Guerrero replies to Iturbide that he rejects the pardon but offers his help if his purpose is really to achieve independence.
At the end of January, Iturbide begins an intense epistolary work to spread its independence plans to various personalities.
On February 4, Iturbide invites Guerrero to meet, which happens on February 10 in Acatempan, municipality of Teloloapan. In this meeting the episode known as Acatempan’s Embrace occurs .
On February 24 Iturbide signs the Iguala Plan and sends it to Viceroy Juan Ruiz de Apodaca. The principles of this document are to establish the independence of Mexico; keep the monarchy headed by Fernando VII or one of the members of the Spanish Crown; establish the Catholic religion as unique, and the union of all social classes.
On March 1, Iturbide announces the Plan of Iguala to the troops that proclaim it as the commander of the Army of the Three Guarantees: Religion, Independence and Union.
Viceroy Apodaca declared Iturbide outlawed, while he added more supporters to his movement.
The Trigarante Army advanced and secured that the independence in several territories of the country was sworn, until its triumphal entry into Mexico City.
On September 28, the Provisional Government Board, which signed the Independence Act, was installed.
In December 1821, a conspiracy is planned in Mexico City, with the purpose of establishing the republic; Miguel Domínguez, Guadalupe Victoria and Nicolás Bravo are involved , among others. The conspirators were imprisoned.