He spent 1915 as Murray's aide until the general's retirement in December. From there, Pratt reported to San Antonio, Texas, in January 1916 as aide to Brigadier General George Bell, Jr.. He accompanied Bell's headquarters to the El Paso District in support of the Punitive Expedition against Pancho Villa in Mexico. There he was promoted to captain, 1st Cavalry, on July 1. In October he was assigned as assistant adjutant of the district.