The Experimental Military Unit (EMU) was a joint Australian-American company-sized helicopter assault force which operated during the Vietnam War. The unit was created in 1967 following a request from the United States military for Australia to send more helicopter pilots to the conflict. As the only available personnel were from the Royal Australian Navy (RAN) Fleet Air Arm (with Australian Army and RAAF pilots already heavily committed), the RAN Helicopter Flight Vietnam (RANHFV) was formed and integrated into the 135th Assault Helicopter Company of the United States Army. The EMU unit name was selected by the Americans as a backronym for the Australian bird, a choice which amused the Australians: despite being large, fast, and highly mobile, the emu cannot fly.
The EMU flew multiple variants of the UH-1 Iroquois helicopter, and was primarily tasked with providing transport and support for units of the Army of the Republic of Vietnam (ARVN), United States Army and Marine Corps, and Australian Army. A typical day's operations consisted of ten transports (supported by four gunships and a command unit) collecting a unit of soldiers, performing a combat assault, then returning the unit to base. Other operations included dawn and dusk assaults, night hunter-killer patrols, and supporting United States Navy SEAL units in the capture of senior Viet Cong personnel. Although the RAN contingent was significantly smaller than the rest of the unit, the Australian personnel frequently found themselves in senior positions, due to having more extensive training and experience than their American counterparts.
Initially operating out of Vung Tau, the EMU was relocated to the Xuân Lộc district at the end of 1967. In late 1968, the unit was moved to near Biên Hòa. In mid-1970, the EMU was tasked to operations into Cambodia, but as the rules of engagement for the Australians forbade them from operating outside Vietnam, the unit operated under-strength for several days until being retasked back to Vietnam operations. Later that year, the unit was relocated to Đồng Tâm. The RANHFV was withdrawn from Vietnam in 1971, ending the joint unit. The Australian contingent was the most heavily decorated RAN unit to serve in the Vietnam War, and the one with the highest casualty rate.