with Marine forces along the DMZ. General Cushman recommended to General
Abrams that General Lam's suggestion be adopted and that he, General
Cushman, would proceed on the premise that the original concept be abandoned
in favor of a revised, more mobile posture.2 Although General Abrams
subsequently accepted General Cushman's recommendation, he suggested
that the South Vietnamese should be eased into both sites after sufficient
As ARVN and Marine commands continued their Duel Blade planning with respect to construction and specific control procedures, General Abrams on 22 October ordered all construction and planning efforts associated with the anti-infiltration effort halted.3 The 1 November bombing halt in the DMZ and North Vietnam, aimed, in part, at restoring the DMZ to a true buffer zone, combined with manpower demands on U.S. forces in the north, made the strongpoint and obstacle barrier system no longer feasible.
Under the new concept, still referred to as Duel Blade, allied forces, supported by air, artillery, and naval gunfire, would, while maintaining a mobile posture, actively resist infiltration from the North by maintaining a comprehensive surveillance effort. While ground reconnaissance inserts would be a part of the effort, attended and unattended detection devices or sensors would provide a majority of the around-the-clock capability. By the end of December, the engineers had implanted three sensor fields in the eastern portion of the DMZ, south of the Ben Hai River.*
At the same time the American command had made rapid progress in the defoliation of a 2,000-meter-wide trace, adjacent to the Laotian border south of the DMZ, which neared completion, and began planning to implant sensors in the western area. Despite these efforts, little evidence existed reflecting a decline in the enemy's intention to continue to use the DMZ for staging troops and supplies, infiltration, and, north of the Ben Hai, as a sanctuary. Marine units, nevertheless, were now under standing orders not to enter the DMZ.
According to the revised concept, the "A" and "C" strongpoint sites considered essential would be used as fire support bases. Those of no value, such as A-3 and C-3, would be closed. With the departure of General Westmoreland in June and the launching of more mobile operations, III MAF halted construction and shifted much of the material set aside for the Duel Blade effort to the construction of an anti-infiltration barrier around Da Nang.
The 1st Brigade, 5th Infantry Division moved south into the populated
coastal sand dune and rice paddy region, covering the districts of Trieu
Phong, Mai Linh, Hai Lang, and Quang Tri City. Here, it found an area
largely devoid of battalion-sized Viet Cong or North Vietnamese Army
units. These units, having suffered a number of decisive defeats, had
retired west into the jungle-covered mountains bordering on Laos. The
remaining Viet Cong and North Vietnamese Army forces continued to maintain
liaison with local force units and the VC infrastructure. They also
continued to move rice and other supplies to main force units further
west. These elements included units of the 808th NVA Battalion
which endeavored to reinforce two local force companies, the C-59 in
Trieu Phong District and the H-99 in Hai Lang District. These two companies,
in an effort to avoid allied capture, had broken down into small groups
of five to six men and tended to operate with village and hamlet guerrilla
forces, which varied in size from cells to squads and in some cases
platoons. Allied intelligence estimates placed Viet Cong strength in
the region, including infrastructure members, at 4,000. Seventy-eight
of the 234 hamlets within the brigade's area of operations were considered
to be under Viet Cong control. Intelligence analysts rated 18 as being
contested and they considered the remainder to be under South Vietnamese
Taking advantage of the absence of Viet Cong and North Vietnamese main force units, Gibson's mechanized brigade concentrated on conducting strike operations. Emphasizing search and clear and cordon and search operations in cooperation and coordination with local forces and the 1st ARVN Regiment, whose area of operation coincided with that of the brigade's, Gibson's troops sought to weed out and destroy the Viet Cong infrastructure. Organized into two infantry and one armored task forces, the 1st Brigade supported the Le Loi campaign and conducted a series of large-scale cordon and search operations and deployed numerous patrols, ambushes, and small "Hunter Killer" teams throughout its new area of operations during the months of November and December. In addition, it provided transportation, hauled construction materials, assisted in road building, and provided security for the long-awaited reset-
* Colonel John F. Mitchell recalled that from July to October 1968,
he was given the task of "establishing the 1st Ground Surveillance Section"
in the 3d Marine Division. According to Mitchell, the group used sensors
with laser technology to track enemy forces. Col John F. Mitchell, Comments
on draft, dtd 5Jan95 (Vietnam Comment File).