Anon. 
After Action Report, Ia Drang Valley Operation, 1st Battalion, 7th Cavalry 14-16 November 1965 

"The Battle of Ia Drang was the first major battle between regulars of the United States Army and regulars of the People’s Army of Vietnam (PAVN / NVA) of North Vietnam during the Vietnam War. The two-part battle took place between November 14 and November 18, 1965, at two landing zones (LZs) northwest of Plei Me in the Central Highlands of South Vietnam (approximately 35 miles south-west of Pleiku) as part of the U.S. airmobile offensive codenamed Operation Silver Bayonet. The battle derives its name from the Drang River which runs through the valley northwest of Plei Me, in which the engagement took place. Ia means "river" in the local Montagnard language.Representing the American forces were elements of the 3rd Brigade, 1st Cavalry Division: the 1st Battalion and 2nd Battalion of the 7th Cavalry Regiment, and the 2nd Battalion, 5th Cavalry Regiment of the United States Army, facing elements of the B3 Front of the PAVN (including the 304 Division) and Viet Cong. The battle involved close air support by U.S. aircraft and a strategic bombing strike by the B-52s. The initial Vietnamese assault against the landing 1st Battalion, 7th Cavalry at LZ X-Ray was repulsed after two days and nights of heavy fighting on November 14-16. However, the follow-up surprise attack on November 17 that overran the marching column of 7th Cavalry 2nd Battalion near the LZ Albany was the deadliest ambush of a U.S. unit during the course of the entire war. About half of some 300 American deaths in the 35-day Operation Silver Bayonet happened in just this one fight that lasted 16 hours."-Wiki