 But as American involvement in Vietnam was winding down , the Army canceled the Cheyenne program on 9 August 1972 . By this time , the AH @-@ 1 Cobra was widely deployed by the Army during the Vietnam War . Controversy with the United States Air Force over the Cheyenne 's role in combat as well as the political climate regarding military acquisition programs had caused the Army to amend the service 's attack helicopter requirements in favor of a twin @-@ engine conventional helicopter , viewed as less technical and more survivable . The Army announced a new program for an Advanced Attack Helicopter ( AAH ) on 17 August 1972 , which led to the development of the AH @-@ 64 Apache . 
