How did Mexico view their army's movement north of the Rio Grande?

It pitted a politically divided and militarily unprepared Mexico against the expansionist-minded administration of U. S. President James K. Polk, who believed the United States had a "manifest destiny" to spread across the continent to the Pacific Ocean.

Explanation:The 1848 Treaty of Guadalupe Hidalgo, forced onto the remnant Mexican government, ended the war and enforced the Mexican Cession of the northern territories of Alta California and Santa Fe de Nuevo México to the United States. Mexico ceded to the United States in 1848, minus Texan claims. The Mexican Cession consisted of present-day U. S. states of California, Nevada, Utah, most of Arizona, about half of New Mexico, about a quarter of Colorado, and a small section of Wyoming.