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.
Emperor of Mexico
With the Declaration of Independence of the Mexican Empire from Spain in 1821, Mexico became an independent monarchy—the First Mexican Empire (1822–1823). Mexico briefly reverted into a monarchy in the 1860s, during the Second Mexican Empire (1864–1867). In both instances of Empire, the reigning Emperor was forcibly deposed and then executed.