General Stephen Watts Kearny, then considered one of the army's most capable officers, received orders by President Polk to lead an expeditionary force to occupy New Mexico and California.
On June 28, his Army of the West marched out of Fort Leavenworth in Missouri. Kearny, the "Father of the U.S. Cavalry", led his soldiers down the Santa Fe Trail and occupied Santa Fe on August 18 without opposition. He then set up a military government in New Mexico.
It was also Kearny's task to protect and convoy American traders' caravans on the trail and to persuade Native American tribes to refrain from their attacks on emigrant trains, either by words or, if necessary, by the demonstration of military power.
