"On July 1, 1965, the 1st Cavalry Division (Airmobile) arrived in Vietnam and suddenly the Huey Helicopters seemed to be everywhere. The first task of the 1st Cavalry was to act as the “eyes and ears” of the division flying up to 100 UH-1Bs. The Huey’s worked in conjunction with the Bell OH-13 scout helicopters, UH-1B transports and the UH-1C gunships..."
Source: http://www.usmilitaryhelicopters.org/helicopter/uh-1-huey