Remember Phoenix?
Hopefully we learned from the mistakes made with Phoenix.
Remember the CIA's Provincial Interrogation Center Program?
Rather effective. From a U.S. Army history:
On the same day the Viet Cong who had been detained were sent to a combined interrogation center established by the Mobile Intelligence Civil Affairs Team and Vietnamese provincial officials at the province capital. Later, the interrogation reports provided information that the enemy elements encountered had been a platoon-size cadre and a newly recruited Viet Cong company. The cadre was reportedly equipped only with small arms, and the company had few weapons. The search for the Viet Cong continued through 5 July and ambushes were again established during the night.
Seems to have worked.