Doctrine leader shares insights with U.S. Border Patrol representatives Friday, April 28, 2023 Lt. Col. Christian Cook, chief, Army Doctrine Proponent Division, Combined Arms Doctrine Directorate, discusses the Army doctrine publishing and implementation process with members of the U.S. Border Patrol on April 27, 2023, at Fort Leavenworth, Kan. (U.S. Army photo by Randi Stenson, MCCoE Public Affairs)