Shaping Mexico

The unstable situation of the Spanish Crown around 1820 led some Royalists in New Spain to reconsider their position towards the civil war in the colony. Agustin de Iturbide, leading a numerous former-royalist army, persuaded rebels who were rather in disorder to get together and fight for independence of Mexico once and for all, if ever with a conservative project contemplating the creation of a Creole Monarchy.

Alter the victory of the so called Three Guarantee Army on the Spanish Royal Army, Mexico became an empire that extended from what today is Costa Rica all the way to the southern part of Oregon on the Northwest and Oklahoma on the Northeast, under emperor Agustin I. One year after the Emperor abdicated, giving in Liberal claims requesting the creation of a Republic. Liberals then decided that the Central American provinces were free to decide their destiny, thus they decided to be independent from Mexico in 1824.

On the contrary, the northern provinces were considered a vast inhospitable land, inhabited by "barbarians". First Mexican presidents promoted the colonization of Texas province by people from the U.S. Some circumstances, such as that of the capital of the province being too far (Saltillo) and the arrival of former convicts as settlers sent by the government, provoked the anger of new Texans.

Finally, when temperamental Santa Anna declared himself president for life on the conservative wing, many provinces declared their independence, Texas among them. Santa Anna declared war to these provinces but they were so many and so revolted that some of them won easily. The Mexican Government never acknowledged Texas independence so when U.S. annexed the territory in 1845, Santa Anna declared war on the U.S.

War lasted two years and ended up with the U.S. victory on a disorganized and scattered Mexican army leaded by Santa Anna. President James Polk authorized the Texan border movement from Nueces River to Bravo River (Rio Grande), then annexed the northern territories including what today is New Mexico, Arizona, California, Nevada, Utah and parts of Oregon, Idaho, Wyoming and Colorado as a war loss compensation.