This episode deals with the efforts of the the US Military, led by General Westmoreland to root out the powerful Viet Cong stronghold west of Saigon called "The Iron Triangle", in addition to areas called "War Zone C" and "War Zone D". Here the Viet Cong built a vast infrastructure of tunnels and war supplies in the villages in the area. The Americans repeatedly carried out large-scale operations attempting to clear this area out. The program shows how the Viet Cong built up this infrastructure, especially their amazing underground cities where they could hold out for long periods of time, even while the Americans were conducting "Search and Destroy" operations on the ground level above them. General Westmoreland's strategy was to try to force the Viet Cong out into the open where the overwhelming superiority of American firepower would win the day, but this program shows how exceedingly difficult this was to execute.
In the end, the relentless American pressure was succeeding in pushing the Viet Cong out of these strongholds and inflicting significant casualties on them. In order to prevent the Viet Cong from returning to this jungle area, large-scale defoliation was carried out by aerial spraying of the toxic Agent Orange, leaving vast areas of this region a lifeless desert. However, the Americans themselves were suffering casualties as well, leaving General Westmoreland frustrated at the slow pace of progress. He wanted a large-scale battle out in the open. No one knew how long this mutual war of attrition could go on nor which side would break first. Finally, the North Vietnamese sponsors of the Viet Cong decided that a massive offensive into the populated centers of South Vietnam would break this cycle of attrition to their advantage. This would become the well-know "Tet Offensive" which is covered in subsequent episodes of this series, and it would finally give General Westmoreland the chance to face the enemy in the way he preferred. Unfortunately for him, it came too late for him to be able to exploit it.