However, the PAVN strategy had tied down large numbers of US troops in the area south of the DMZ, leaving population centers under-protected.

The tactical goal of these incursions was to draw United States military forces away from cities and towns; a similar strategy would be employed during the final months of 1967 in order to maximize the impact of the upcoming Tet Offensive.

In response, the Marines elected to construct and reinforce a string of firebases south of the DMZ at Con Thien, Gio Linh, Camp Carroll, and Dong Ha.

In addition to these firebases, U.S. forces also established an interconnected sequence of electronic sensors and other detection devices called the McNamara Line.

[9] The preliminary plan centered on the insertion of four to five man "stingray" teams along the suspected enemy avenues of approach.

In the event that ground reinforcements were needed the infantry companies located at Cam Lộ and Dong Ha would provide them.

[8] Shortly after landing the team could smell smoke from a suspected enemy camp and soon reported PAVN movement along trails near their position.

Team Groucho Marx called for an artillery bombardment from Cam Lo on the location on two occasions over the next days.

[8]: 177–9 [10] On the morning of 8 August 1966, the team spotted approximately 15 enemy troops moving in a skirmish line in search of the American patrol.

Eight UH-34 helicopters from HMM-161 arrived at the improvised landing zone without incident, but upon takeoff PAVN troops opened fire from a ridgeline to the north.

Now under the command of Captain Howard V. Lee, the Marines that remained set up a defensive perimeter and fought off several large attacks from what is estimated to have been a company of enemy soldiers.

[8]: 177–9 [10] Over the course of the next few hours Major Vincil W. Hazelbaker landed his UH-1E helicopter under withering enemy fire to resupply the Marines.

Hazelbaker then assumed command, as Lee had been injured by a fragmentation grenade, and directed a napalm strike on the enemy position at dawn on 9 August 1966.

Reinforcements finally arrived later that morning, secured the area, and aided in the evacuation of the remaining Marines in the afternoon.

On 19 August Company E located two concrete bunkers and was moving to destroy them when they were caught in a machine gun crossfire.

At 14:00 they found a bowl shaped area honeycombed with large caves that showed signed of recent PAVN occupation.

The tank guns, together with recoilless rifle fire, blasted the PAVN positions, breaking through to Companies E and F by mid-morning.

However, some PAVN soldiers penetrated the perimeter before the flares were fired, attacking the positions where the 3rd Battalion, 12th Marines artillery had been located only the previous day.

On the morning of 8 September Company G engaged a PAVN platoon in a three-hour firefight 1 km northeast of Con Thien, losing five Marines killed.

[11][8]: 188–9 U.S. intelligence indicated that the 324B Division was continuing to build up its infiltration routes north of the Rockpile and through the Núi Cây Tre Ridge.

Air and artillery support was called in and a two and a half day battle ensued before the arrival of 2/7 Marines marching from Cam Lộ forced the PAVN to disengage.

[8]: 190–1 On the morning of 22 September, after bombarding a false target area, CH-46s began landing troops from the 3rd Battalion, 4th Marines 4.5 km east of the Núi Cây Tre.

At 07:30 on 27 September, as Company K moved towards its next objective 1 km southwest it was ambushed by the PAVN losing seven dead and one missing.

3/4 Marines commander Lieutenant Colonel William J. Masterpool ordered the battalion to move up to join Company K and establish a defensive perimeter.

Attempts at frontal and flanking assaults failed due to the steep terrain and heavy fire, and the Marines withdrew to allow air and artillery strikes.

3rd Marine Division deputy commander BG Lowell English strongly opposed the plan stating "When you're at Khe Sanh, you're not really anywhere.

In late October Task Force Delta was deactivated but English retained control of the operation from Dong Ha.

[9] One of the other purposes of Operation Prairie was to reduce the large investment of manpower that the U.S. forces had committed to protect the DMZ.

Instead the PAVN strategy tied down a major portion of the Marine force in I Corps along the vast, barren tracts of land south of the DMZ, leaving population centers undermanned and under protected.

[15] This article incorporates public domain material from websites or documents of the United States Marine Corps.