Project Dye Marker

Project Dye Marker also nicknamed McNamara's Wall (after the Secretary of Defence Robert McNamara) or the Electric Fence was the third and final name for an electronic infiltration barrier constructed by the American forces in Quang Tri Province, Vietnam and intended to curb the transport of North Vietnamese troops and supplies through the Demilitarized Zone along the Ho Chi Minh trail during the Vietnam War.

The barrier ran from the South China Sea to Laos, just south of the Demilitarized Zone, had a total length of 76 kilometers (47 miles). Construction work was scheduled to start in late 1967 or early 1968 and was carried out by the 3rd Marine Division. Stretches of the barrier were under radar surveillance, others were secured by trip wires, mine fields, and barbed-wire entanglements.

The intended effect of the barrier was to curb infiltration of South Vietnam by northern forces, which would have allowed it to scale back the American bombing of North Vietnam. However, it was criticized at the time of its inception already for keeping American troops in static positions while facing mobile enemy forces.

References

• "Alarm Belt", article in Time Magazine, Friday, September 15, 1967
• Short note on Project Dye Marker by the Vietnam Helicopter Pilots Association