The 509th Infantry Regiment is an Airborne Infantry regiment of the United States Army. Previously titled the 509th Parachute Infantry Regiment or 509th (PIR), this battalion was activated at fort Benning, Georgia as the 504th Parachute Infantry Battalion in October 1941. Nicknamed "Geronimo", the 509th conducted the U.S. Army's first combat jump during World War II, flying 1500 miles from England to seize Tafarquay airport in Oran, Algeria on 8 November 1942. In total, the 509th made five combat jumps during the war.
Currently, 1st and 3rd battalion remain active. The 1st Battalion serves as the Opposing Force (OPFOR) at the U.S. Army's Joint Readiness Training Center at Fort Polk, Louisiana. The 3rd Battalion is assigned to the 4th Brigade Combat Team (Airborne), 25th Infantry Division, at Fort Richardson, Alaska. Since its inception, the 509th Infantry Regiment has forged its unit identity by operating in perpetual independence from larger Airborne units like the 82d and 101st Airborne Divisions.