The 15th Cavalry Division was created with the 1st & 2nd Cavalry Brigades in February 1917 at Fort Sam Houston, Texas. It numbered in succession of the 1st–14th Divisions, which were not all active at its creation. Originally trained for deployment to Europe, its units were later converted into field artillery units. The division was deactivated on 12 May 1918. Elements of the division were reconstituted as the 1st Cavalry Division in 1920.