Indigenous peoples of Mexico
When Mexico gained independence in 1821, the casta system was eliminated as a legal structure, but racial divides remained. 
White Mexican argued about what the solution was to the "Indian Problem", that is indigenous who continued to live in communities and were not integrated politically or socially as citizens of the new republic. The Mexican constitution of 1824 has several articles pertaining to indigenous peoples. The second article of the constitution of Mexico recognizes and enforces the right of indigenous peoples and communities to self-determination and therefore their autonomy to:
Mexican–American War
The Mexican Army emerged from the war of independence (1810–1821) as a weak and divided force. Before the war with the United States, the military faced both internal and foreign challenges. The Spanish still occupied the coastal fortress of San Juan de Ulúa, and Spain did not recognize Mexico's independence, so that the new nation was at risk for invasion. In 1829, the Spanish attempted to reconquer their former colony and Antonio López de Santa Anna became a national hero defending the homeland. The army had a set of privileges ("fueros"), established in the colonial era, that gave it jurisdiction over many aspects of its affairs. In general, the military supported conservative positions, advocating for a strong central government and upholding privileges of the military and the Catholic Church.