troops could detect the general location of a sensor, they immediately began to search out others and destroy them. Another response was to simply avoid them. The final evolution of anti-sensor measures was to attempt to deceive them. The chief protection of the sensors proved to be the dense foliage that covered the majority of the logistical system. Operations in South Vietnam While the electronic barrier program in Laos became the most visible part of the anti-infiltration program, the physical barrier project in South Vietnam was largely abandoned after 1968 in favor of mobile operations. The SPOS outlined in the original Dyemarker plan envisioned a virtual defensive wall stretching from the South China Sea to Dong Ha Mountain. The plan called for a fence, a line of twin steel apron and barbed steel tape, an anti-personnel mine field, a passive sensor detection system, and another line of twin steel apron and barbed steel tape, to "trace" this path, providing a physical obstacle to enemy infiltration. Observation posts and towers would line the route, and six specifically designed strong points would be constructed, with associated battalion base areas. A combined force of a single US Marine Corps Regiment and a single ARVN Regiment were to man these positions. The 3rd Naval Construction Battalion designed fighting and living bunkers for the route, presenting them for tests and evaluation 1968, both in CONUS and in Vietnam. Also, 28 January 1968, COMUSMACV provided its own guidance for the planned creation of the ARVN Dyemarker Regiment. COMUSMACV envisioned a Regiment of 5 4-company Battalions and an Armored Cavalry Squadron. On 30 January, COMUSMACV informed the commander of III MAF of their proposed mission to augment the proposed ARVN force manning the barrier. The ARVN 2nd Regiment, of its 1st Infantry Division became earmarked for the barrier mission. On 29 October 1968, work was stopped on the physical SPOS barrier, by that time redesignated as Duel Blade, under MACV Planning Directive 10–67, citing changes in the overall force posture, both enemy and friendly. The physical barrier would be replaced by the revised Duel Blade plan of active resistance utilizing air strikes, artillery and naval bombardment and mobile reaction forces. Base sites already constructed or under construction were to be used as support bases for the revised operation plan. Other applications Though Igloo White's primary focus was monitoring traffic along the Ho Chi Minh Trail, the DCPG's