On 17 March 1917, the entire 3rd Cavalry Regiment was transferred to Fort Sam Houston, Texas, and one month later, the United States of America entered the First World War on the side of the Allies. The regiment was one of the first units to arrive in France in November of that year, and immediately began their duties; the operation of three major horse remount depots. The three squadrons were charged with the purchase of horses, mules and forage, the care, conditioning, and training of remounts before issue, and the distribution and issue of remounts to the American Expeditionary Force. The only 3rd Cavalry unit to see action in World War I was K Troop, detached from 3rd Squadron, the Troop served in I Corps during the Aisne-Marne Offensive (18 July – 6 August 1918), and in III Corps on the Vesle Front (7-17 August), the Oise-Aisne Offensive (18 August – 9 September), and the Meuse-Argonne Offensive (14 September – 11 November).