Following the cancellation of the AH-56 Cheyenne in 1972, in favor of projects like the U.S. Air Force A-10 Thunderbolt II and the Marine Corps AV-8A Harrier, the United States Army sought an aircraft to fill an anti-armor attack role that would still be under Army command. The 1948 Key West Agreement forbade the Army from owning combat fixed-wing aircraft. The Army wanted an aircraft better than the AH-1 Cobra in firepower, performance and range. It would have the maneuverability for terrain following nap-of-the-earth (NoE) flying. To this end, the U.S. Army issued a Request For Proposals (RFP) for an Advanced Attack Helicopter (AAH) on 15 November 1972. As a sign of the importance of this project, in September 1973 the Army designated its five most important projects as the "Big Five", with the AAH included.