Battle of Ia Drang - Wikipedia

On November 14, 1965, the Battle of the I Drang Valley began. It would last four days. From the article:

The Battle of Ia Drang was the first major battle between the United States Army and the People's Army of Vietnam (PAVN), also referred to as the North Vietnamese Army (NVA), and was part of the Pleiku Campaign conducted early in the Vietnam War. It comprised two main engagements, centered on two previously scouted helicopter landing zones (LZs), known as LZ X-Ray and LZ Albany. The first involved the 1st Battalion, 7th Cavalry Regiment and supporting units under the command of Lieutenant Colonel Hal Moore, and took place November 14–16, 1965 at LZ X-Ray, located at the eastern foot of the Chu Pong massif in the central highlands of Vietnam. The second engagement involved the 2nd Battalion, 7th Cavalry Regiment plus supporting units under the command of Lieutenant Colonel Robert McDade, and took place on November 17 at LZ Albany, farther north in the Ia Drang Valley. It is notable for being the first large scale helicopter air assault and also the first use of Boeing B-52 Stratofortress strategic bombers in a tactical support role. Surrounded and under heavy fire from a numerically superior force, the American forces at LZ X-ray were able to hold off and drive back the North Vietnamese forces over three days of battle, largely through the support of both air power and heavy artillery bombardment, which the North Vietnamese lacked. LZ X-ray was considered an American tactical victory, as the Americans were able to exact an almost 10:1 kill ratio. At LZ Albany, the American forces were ambushed in close quarters. They were unable to use air and artillery support due to the close engagement of the North Vietnamese, the American forces were badly defeated, suffering an over-50% casualty rate before being extricated from the battle. Both sides, therefore, were able to claim victory in the battle.

The size of the clearing at LZ X-Ray meant that troops had to be shuttled in, the first lift landing at 10:48. The last troops of the battalion were landed at 15:20, by which time the troops on the ground were already heavily engaged, with one platoon cut off. Faced with heavy casualties and unexpected opposition, 1st Battalion was reinforced by B Company 2nd Battalion 7th Cavalry. Fighting continued the following day when the LZ was further reinforced by A Company 2/7 and also by 2nd Battalion 5th Cavalry, and the lost platoon was rescued. The last Vietnamese assaults on the position were repulsed on the morning of the 16th. As the Vietnamese forces melted away, the remainder of 2/7 and A Company of 1st Battalion 5th Cavalry arrived. By mid-afternoon 1/7 and B Company 2/7 had been airlifted to LZ Falcon, and on the 17th of November 2/5 marched out towards LZ Columbus while the remaining 2/7 and 1/5 companies marched towards LZ Albany. The latter force became strung out and, in the early afternoon, were badly mauled in an ambush before they could be reinforced and extricated.

The battle at LZ X-Ray was documented in the CBS special report Battle of Ia Drang Valley by Morley Safer and the critically acclaimed book We Were Soldiers Once... And Young by Harold G. Moore and Joseph L. Galloway. In 1994, Moore, Galloway and men who fought on both the American and North Vietnamese sides, traveled back to the remote jungle clearings where the battle took place. At the time the U.S. did not have diplomatic relations with Vietnam. The risky trip which took a year to arrange was part of an award-winning ABC News documentary, They Were Young and Brave produced by Terence Wrong. In 2002, Randall Wallace depicted the battle at LZ X-Ray in the 2002 movie We Were Soldiers starring Mel Gibson and Barry Pepper as Moore and Galloway, respectively. Galloway later described Ia Drang as "the battle that convinced Ho Chi Minh he could win".