Not only the jungle was a major obstacle for the mobility of troops in Vietnam, but also its mountainous terrain. Before the involvement of the U.S. in Vietnam, a high ranking officer dubbed Vietnam "a nightmare terrain for maneuvers." In anticipation to the participation of U.S. troops in the conflict between South and North Vietnam, the U.S. Army ordered the test of helicopters as an alternative to wheeled-vehicles for the transport of troops, weapons, ammunition, supplies and wounded personnel and casualties. The unit designated for the study of the effective use of the helicopter was the 1st Division of Cavalry, which had served in World War II equipped with tanks instead of horses. Once the tactics of "air mobility" were tested and proved, the division received the name of "1st Air Cav", and all of its units became famous in Vietnam as merely "Air Cav."
After the Air Cav division demonstrated the efficiency of air mobility supported by helicopters, other units in the army were trained in their use as well as some units of the Marine Corps.
This was an armed uprising that took place in Massachusetts when four thousand rebels were led by Daniel Shays, a veteran from the Revolutionary War to protest against what they perceived as economic and civil rights injustices
