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?

Robert Strange McNamara (June 9, 1916 – July 6, 2009) was an American business executive and the eighth Secretary of Defense, serving from 1961 to 1968 under Presidents John F. Kennedy and Lyndon B. Johnson.  He played a major role in escalating the United States involvement in the Vietnam War.  McNamara was responsible for the institution of systems analysis in public policy, which developed into the discipline known today as policy analysis. <SEP> Project Dye Marker was a cover name for a strong point/obstacle component of the electronic anti-infiltration barrier system in South Vietnam known as "McNamara Line" during the Vietnam War, which aimed to create an alternative to the US bombing of North Vietnam.  The fortifications were partially constructed by the American forces in 1967-1968 along the eastern portion of the demilitarized zone.  An effective anti-infiltration barrier, running across South Vietnam deep into Laos, was a grand vision of the US Secretary of Defence Robert McNamara, who feared that escalation of bombing can bring greater Chinese involvement, and a vital component of his operational strategy.  It was an enormous multimillion project, which was nicknamed in the media as the Great Wall of Vietnam, McNamara's Wall, McNamara Barrier, Electric Fence, and Alarm Belt. <SEP> 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 McNamara Line ran across South Vietnam from the South China Sea to the Laotian border along the Vietnamese Demilitarized Zone (DMZ).  The eastern part included fortified field segments with Khe Sanh as linchpin, along with stretches, where roads and trails were guarded by the high-tech acoustic and heat-detecting sensors on the ground and interdicted from the air.  Named "the barrier system" by Robert McNamara, it was one of the key elements, along with gradual aerial bombing, of his war strategy in Vietnam.  A sophisticated electronic surveillance was backed with assorted types of mines, including so-called gravel mines, and troops at choke points. <SEP> Vadim Petrovich Shcherbakov was an officer in the Soviet Air Defense Forces (PVO Strany).  As a senior lieutenant, he was serving in the 260th "Bryansky" Anti-Aircraft Missile Regiment.  In 1966-1967 Shcherbakov's whole regiment was temporarily assigned as a Group of Soviet Military Advisors in Vietnam () and in March 1966 was transferred to North Vietnam, where the regiment was tasked with establishing a training center and training the NVA's 274th Anti-Aircraft Missile Regiment for combat duty.  In North Vietnam Shcherbakov served as a SAM operator/instructor, and specialized as a fire control operator during combat deployments.  For his service Shcherbakov received the Order of Lenin, the highest Soviet decoration after returning from North Vietnam in 1967.  in their 18th report claims that formerly closed soviet sources credited Col Shchbakov with 10 combat engagements and 6 kills.  After Vietnam, Shcherbakov continued his service, eventually reaching the rank of Colonel.  Very little is known about his biography except for multiple brief mentions in Soviet Officers' Vietnam War memoirs.  He was still alive in 1991, when he was attending an annual meeting of the Russian Association of Vietnam War veterans.  He was a retired Colonel at that time.