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.
Republic of Texas
The region of the Mexican state of Coahuila y Tejas commonly referred to as Mexican Texas declared its independence from Mexico during the Texas Revolution in 1836. The Texas war of independence ended on April 21, 1836, but Mexico refused to recognize the independence of the Republic of Texas, and intermittent conflicts between the two states continued into the 1840s. The United States recognized the Republic of Texas in March 1837 but declined to annex the territory.