Spanish attempts to reconquer Mexico
Mexican independence was officially achieved on September 27, 1821, under the Treaty of Córdoba. Spain did not recognize the treaties, arguing that the viceroy Juan O'Donojú had no authority to recognize the independence of any overseas province. This situation was dangerous to the newly acquired independent status of the nation, which had not yet been recognized by any of the European powers that could support it, and the threat of Spanish reconquest was a constant worry to the leaders of the nascent regime. On May 13, 1822 decrees were issued by the government to imprison anyone who conspired against Mexico's independence.
Agustín de Iturbide
Early in the independence period of Mexico's history, even the day used to mark Independence would be based on one's side. Traditionalists favored 27 September to celebrate, when Iturbide entered Mexico City, but liberal politicians preferred 16 September to celebrate Hidalgo's call for rebellion against Spain.