U.S. and South Vietnamese forces battle North Vietnamese troops for Ap Bia Mountain (Hill 937), one mile east of the Laotian border. The battle was part of Operation Apache Snow, a 2,800-man Allied sweep of the A Shau Valley. The purpose of the operation was to cut off North Vietnamese infiltration from Laos and enemy threats to Hue and Da Nang. U.S. paratroopers pushing northeast found the communist forces entrenched on Ap Bia Mountain. In fierce fighting directed by Maj. Gen. Melvin Zais, the mountain came under heavy Allied air strikes, artillery barrages, and 10 infantry assaults. The communist stronghold was captured on May 20 in the 11th attack, when 1,000 troops of the 101st Airborne Division and 400 South Vietnamese soldiers fought their way to the summit of the mountain.
During the intense fighting, 597 North Vietnamese were reported killed and U.S. casualties were 56 killed and 420 wounded. Due to the bitter fighting and the high loss of life, the battle for Ap Bia Mountain was dubbed "Hamburger Hill" by the U.S. media.