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 dominant figure of the second quarter of 19th century Mexico was the dictator Antonio López de Santa Anna. During this period, many of the territories in the north were lost to the United States. Santa Anna was the nation's leader during the conflict with Texas, which declared itself independent in 1836, and during the Mexican–American War (1846–48). One of the memorable battles of the U.S. invasion of 1847 was when a group of young Military College cadets (now considered national heroes) fought to the death against a large army of experienced soldiers in the Battle of Chapultepec (September 13, 1847). Ever since this war many Mexicans have resented the loss of much territory, some by means of coercion, and more territory sold cheaply by the dictator Santa Anna (allegedly) for personal profit.