If the Marines could not be smashed, and the Communists had tried several times, they had to be diverted or thinned out. The answer to the enemy's dilemma lay along the 17th Parallel. Gradually, they massed large troop concentrations within the Demilitarized Zone (DMZ), in Laos, and in the southern pan-handle of North Vietnam; in short, they were opening a new front. Nguyen Van Mai, a high Communist official in Phnom Penh, Cambodia, predicted: "We will entice the Americans closer to the North Vietnamese border and ... bleed them without mercy." That remained to be seen.(3) In response to the enemy buildup along the DMZ throughout the summer and fall of 1966, General Walt shifted Marine units further north. The 3d Marine Division Headquarters moved from Da Nang to Phu Bai, and a Division Forward Command Post (CP) continued to Dong Ha so that it could respond rapidly to developments along the DMZ. In turn the 1st Marine Division Headquarters moved from Chu Lai to Da Nang and took control of operations in central and southern I Corps. For specific, short-term operations, the division commanders frequently delegated authority to a task force headquarters. The task force was a semipermanent organization composed of temporarily assigned units under one commander, usually a general officer. Because of the fluid, fast-moving type of warfare peculiar to Vietnam, the individual battalion became a key element and went where it was needed the most. It might operate under a task force headquarters or a regiment other than its own parent unit. For example, it would not be uncommon for the 2d Battalion, 9th Marines to be attached to the 3d Marines while the 2d Battalion, 3d Marines was a part of another command. Commitments were met with units that were the most readily available at the time.(4) With the buildup of American troops in Quang Tri province, there logically followed the buildup of installations. Dong Ha was the largest since it served as the brain and nervous system of the entire area. Eight miles to the southwest was Camp J. J. Carroll, a large artillery base. The Marine units there were reinforced by several batteries of U. S. Army 175mm guns which had the capability of firing into North Vietnam. Located at the base of a jagged mountain ten miles west of Camp Carroll was another artillery base--the Rockpile. This facility also had 175mm guns and extended the range of American artillery support almost to the Laotian border. In addition, the Marines built a series of strongpoints paralleling and just south of the DMZ. Gio Linh and Con Thien were the two largest sites. (See Map 2).