Wanderlust World Wanderlust World Mexico's resentment toward the 1845 U.S. annexation of Texas was profound, rooted in a cascade of political, territorial, and national honor grievances that made war nearly inevitable.
After winning independence from Spain in 1821, Mexico struggled to populate and govern its vast northern territories. To develop Texas, the Mexican government initially encouraged Anglo-American settlement under empresario grants (Stephen F. Austin's colony being the most famous). Settlers agreed to become Mexican citizens, convert to Catholicism, and abide by Mexican law.
Despite Mexican protests, the U.S. Congress approved annexation via joint resolution (March 1845); Texas voters ratified it (October 1845). Mexico severed diplomatic relations. When U.S. troops under Zachary Taylor moved into the disputed Nueces Strip (between the Nueces River and Rio Grande), Mexican forces attacked—providing the pretext for the U.S. declaration of war (May 1846).
The Mexican–American War (1846–48) ended in catastrophic defeat for Mexico. The Treaty of Guadalupe Hidalgo (1848) forced Mexico to cede ~55% of its prewar territory—present-day California, Nevada, Utah, most of Arizona and New Mexico, plus parts of Colorado and Wyoming—in exchange for $15 million. Thousands of Mexican soldiers and civilians perished.
The annexation wasn't merely a territorial dispute; it struck at Mexico's sovereignty, national dignity, and survival as a republican experiment. The wound shaped Mexican identity and U.S.–Mexico relations for generations.