Project Dye Marker

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Operation Dye Marker
Part of the Vietnam War
Flag of the United States.svg United States Flag of Vietnam.svg Democratic Republic of Vietnam (North Vietnam)

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,[1] 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,[2] McNamara's Wall, McNamara Barrier,[3] Electric Fence, and Alarm Belt.[4]


The Dye Marker defensive line project, previously called Practice Nine and Illinois City, stretched along the demilitarized zone starting from the South China Sea, and had a total length of 76 kilometers (47 miles). Some parts of the defensive line were manned and equipped with the bunkers, outposts, reinforcing and fire support bases, surrounded by concertina wire. Other segments were under constant radar, motion and acoustic surveillance, and secured by trip wires, mine fields, and barbed-wire entanglements. The airborne receiving equipment carried by EC-121R's relayed the signals and triggered artillery and bombers responses.[5][6]

The plans that were leaked to the media called for an inexpensive barbed wire fence with watch towers, and they were presented to the public as a trivial measure, while the electronic part was highly classified. In reality, the strong-point part of the anti-infiltration system in Quang Tri Province, Vietnam was reinforced with electronic sensors and gravel mines to stop the flow of North Vietnamese troops and supplies through the demilitarized zone during the decisive years of the Vietnam War.[4] Construction was announced on September 7, 1967, and was carried by the 3rd Marine Division. First, the 11th Engineers started to work on bulldozing the so-called Trace, a path 600 meter wide and 11 kilometers long that was stripped of trees, brush and villages if needed. The backbone of the strong-point system were fortified bases Alpha 2 at Gio Linh on the east, Alpha 4 at Con Thien on the west, and Alpha 3 in between.[7] 7,578 American marines have been deployed in support of Dye Marker strong point/obstacle system by 1 November 1967. In addition, 4,080 American troops have been involved in the air-supported anti-infiltration part of Dye Marker.[8]:4

Other code names[edit]

On September 13, 1967, the project's Dye Marker name was switched to Muscle Shoals, and in June 1968 it was changed again, this time to Igloo White.[5]:139


The strategic meaning of the Dye Marker, as well as a whole McNamara Line, which were to stretch westward into Laos, was to curb the infiltration of South Vietnam by the NVA forces. This would have allowed McNamara to scale back the American bombing of North Vietnam and start negotiations with Hanoi.[9] However, the Tet Offensive demonstrated the futility of such plans.

The defensive barrier system was also criticized at the time of its inception for keeping American troops in static positions while facing mobile enemy forces.[8] After the Tet Offensive, the criticism intensified, and Senator Stuart Symington (D-Missouri) called the barrier a "billion dollar Maginot line concept".[10]

See also[edit]


  1. ^ Memorundum: Evaluation of Alternative Programs for Bombing North Vietnam. Central Intelligence Agency, 1 June 1967. PDF
  2. ^ The Great Wall of Vietnam[permanent dead link], Science Digest, April 1968.
  3. ^ McNamara Barrier May Be Expanded. The Boston Globe, Oct 14, 1968, p. 7.
  4. ^ a b "Nation: Alarm Belt", Time Magazine, Friday, September 15, 1967.
  5. ^ a b Sikora, Jack, and Larry Westin. Batcats: The United States Air Force 553rd Reconnaissance Wing in Southeast Asia. Lincoln, NE: IUniverse, Inc, 2003.
  6. ^ Wilson, George, C. Yanks Mull Further Work on McNamara Red Barrier. The Spokesman-Review, October 14, 1968, p. 1.
  7. ^ Alpha Bases Along the DMZ Companion website to DMZ DIARY by Jeff Kelly
  8. ^ a b Memo for Mr. Rostow from Gen E. G. Wheeler from Aqust 30, 1967. Declassified on Feb. 24, 1983. The Vietnam Center and Archive at Texas Tech University.
  9. ^ Drea, Edward J. McNamara, Clifford, and the Burdens of Vietnam, 1965-1969. Archived 2013-10-29 at the Wayback Machine Washington, D.C.: Historical Office, Office of the Secretary of Defense, 2011.
  10. ^ North Viet Infiltration a Mystery: Pentagon Mum on DMZ Setup. The Spokesman-Review, May 9, 1968, p. 1.

External links[edit]