At the commencement of hostilities between American and Mexican forces, General Zachary Taylor asked the Texas government to mobilize troops for the war.

William Gordon Cooke, the adjutant general of Texas, called for two regiments of cavalry to serve for six months, furnishing their own weapons and horses.

[1] The first to enlist was a quickly organized company of 26 men from Corpus Christi under the Ranger captain Samuel Hamilton Walker, which mustered into federal service in April 1846.

The Ranger captain John Coffee Hays began to mobilize the newly reorganized Texas frontier militia companies, recruiting them up to strength to fill the requirements for a mounted regiment.

His men were mustered into federal service in June and July 1846[2] as the First Regiment of Texas Mounted Rifle Volunteers, a part of Zachary Taylor's Army of Occupation.

Worth started on 20 September along with Hays's Texas Rangers screening the advance, but they camped for the night three miles from the Saltillo road.