Mobilization of the Alabama National Guard for service on the Mexican border was announced on June 16, 1916. It included five regiments, the largest being the 4th Alabama, and had been created as militia by the Alabama legislature in 1911. Alabamians regarded the 4th Alabama as the descendant of a Confederate unit with the same name and number. There had not been a 4th Alabama between the end of the Civil War in 1865 and 1911.
The newly activated unit was assembled at Vandiver Park, the racetrack in Montgomery, Alabama, in late June, and was placed under the command of Major William Preston Screws, a regular army officer. As a captain he had supervised their earlier training and summer camps since 1913. After mobilization he led the 4th Alabama through basic infantry training at Vandiver Park from July 4, 1916 to October 22, 1916.
Major Screws then took about 1,300 officers and men by train to Nogales, Arizona and conducted advanced infantry training there until March, 1917. The regiment returned to Montgomery and performed guard duty for a month and a half at railroad and industrial sites throughout Alabama.
The First Infantry Regiment was officially organized in 1881 from several volunteer militia units. The regiment was called to active duty during the Spanish-American War in 1898. It served at the Mexican Border in 1916 and 1917 in response to Pancho Villa's invasion. In 1917 Sept. the regiment became the 123rd U.S. Infantry and was mustered into Federal service at Camp Wheeler, Georgia.