In this March 1965 file photo shot by Associated Press photographer Horst Faas, hovering U.S. Army helicopters pour machine gun fire into the tree line to cover the advance of South Vietnamese ground troops in an attack on a Viet Cong camp 18 miles north of Tay Ninh, Vietnam, northwest of Saigon near the Cambodian border.  (AP Photo/Horst Faas, File)

Photo by: HORST FAAS

In this March 1965 file photo shot by Associated Press photographer Horst Faas, hovering U.S. Army helicopters pour machine gun fire into the tree line to cover the advance of South Vietnamese ground troops in an attack on a Viet Cong camp 18 miles north of Tay Ninh, Vietnam, northwest of Saigon near the Cambodian border. (AP Photo/Horst Faas, File)