Project Dye Marker was a cover name for an electronic anti-infiltration barrier system with a strong point/obstacle component. It was partially constructed by the American forces in 1967-1968 in South Vietnam along the eastern portion of the demilitarized zone. Some stretches of the defensive line were manned and equipped with the bunkers, outposts, reinforcing and fire support bases, surrounded by concertina wire. Other parts were under constant radar, motion and acoustic surveillance, and secured by trip wires, mine fields, and barbed-wire entanglements. Anti-infiltration barrier was a vital part of a strategic program unofficially referred to as McNamara Line, (after the Secretary of Defence Robert McNamara), running across South Vietnam deep into Laos. McNamara Line was a grand scale,