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.
Military history of Mexico
The war for independence lasted eleven years until the troops of the liberating army entered Mexico City in 1821. Thus although independence from Spain was first proclaimed in 1810, it was not formalized until 1821, under the Treaty of Córdoba, which was signed on September 16 in Córdoba, Veracruz, by the Spanish viceroy Juan de O'Donojú and Agustín de Iturbide, ratifying the Plan de Iguala.