Vietnam and its allies in South Vietnam, known as the Viet Cong, against the government of South Vietnam and its principal ally, the United States. Called the “American War” in Vietnam
Hamburger Hill was the scene of an intense and controversial battle during the Vietnam War. Known to military planners as Hill 937 (a reference to its height in meters), the solitary peak is located in the dense jungles of the A Shau Valley of Vietnam, about a mile from the border with Laos.
During the Vietnam War, the U.S military engaged in an aggressive program of chemical warfare codenamed Operation Ranch Hand American forces used more than 20 million gallons of herbicides in Vietnam
The Vietcong and U.S army had the tunnels to  travel without being seen and to keep supply's and sometimes the enemy tries to sneak in 
The U.S army would enter Vietnam villages and search for Vietcong soldiers and if people would refuse then they would burn down building
As a result of advances gas warfare the U.S army used it  to kill most of the Vietcong soldiers resulting in the end of the Vietnam war