President James K. Polk desired to achieve his vision of "Manifest Destiny," and sought to acquire Mexico's northern territories. Mexico had no desire to sell Alta California and Nuevo Mexico to Pres. Polk, and in turn was provoked into war by attacking American troops within disputed territory in Texas. From 1846-1848, the United States and Mexico fought for supremacy of these territories. Modern historians view the Mexican-American War as a source of controversy due to how the land was acquired. Learn how the United States was able to expand from east to west with History In A Nutshell!