The AH-56 Cheyenne was not used during Vietnam. It was never going to be used in Vietnam. It was to being built to help combat the threat in Europe from the large number of Soviet tanks if Russians ever attacked. It was being designed as a high speed tank killer. In the Vietnam war the North Vietnamese didn't have a large number of tanks. Just for my own info was this pic of the Cheyenne in Operation Flashpoint Resistance someones add on?