Question: The McNamara Line was an operational strategy employed by the United States in 1966–1968 during the Vietnam War to prevent infiltration of South Vietnam by NVA forces from North Vietnam and Laos, the sophisticated electronic surveillance was backed with assorted types of mines, named "the barrier system" by Robert Strange McNamara, was an American business executive and the eighth Secretary of Defense, serving from 1961 to what year?
Answer: 1968