This historical fact was researched by John-Al Skimbo, 48th AHC (66)
The first U.S. battalion-size night combat assault took place on 31 October 1966 when the combat elements of the 2nd Battalion, 327th Infantry (Airborne), 101st Airborne Division, were lifted into two landing zones near Tuy Hoa by the 48th and 129th Assault Helicopter Companies and the 179th Assault Support Helicopter Company of the 10th Combat Aviation Battalion. Twenty-four UH-1D, six UH-1B, and four CH-47 helicopters were used. The night before, the 10th Combat Aviation Battalion had conducted a deception operation involving a simulated night comabt assault with preparatory fire by tactical air, artillery, and gunships and with illumination by flares. The actual operation was executed without preparatory fire and illumination. Pathfinders and security elements were positioned in the landing zones prior to the main assaults. Helicopters flew nap-of-the-earth flight paths to gain further surprise."
SOURCE: Vietnam Studies, Tactical and Materiel innovations, by Lieutenant General John H. Hay, Jr., Department of the Army, Washington, D.C., 1974