From a psychological operations perspective, "The Vietnam War Phoenix Program is controversial to this day. Supporters say that it was a legal and closely controlled US-Vietnamese intelligence program aimed at destroying the Viet Cong infrastructure, while the critics say that it was an illegal system of arresting, torturing and murdering innocent Vietnamese civilians...
"Military Assistance Command Vietnam (MACV) Directive 381-41, dated 9 July 1967, inaugurated the Intelligence Coordination and Exploitation (ICEX) program to Attack the Viet Cong Infrastructure (VCI). In late 1967, MACV replaced the name “ICEX” with “Phoenix,” after a mythical bird that appeared as a sign of prosperity and luck and a near translation of the South Vietnamese name for the program, “Phung Hoang” (All-seeing bird”)."
As early as 1964, GEN William Westmoreland, commander of Military Assistance Command Vietnam (MACV) "knew that he lacked the forces to wage both a war of attrition and one of pacification, so he chose the former. The argument over whether or not this was the right course of action will likely go on forever, but undoubtedly the shape of the war changed dramatically after the Tet Offensive. The enemy was badly mauled and, despite the political gains made, militarily lost the initiative for quite some time." 
When the VC regrouped after the Tet Offensive, "Westmoreland never had such an advantage. When American ground forces entered the war in 1965, they faced an enemy on the offensive, but in June 1968 the new MACV commander, General Creighton Abrams, confronted an enemy on the ropes. Abrams plainly recognized his advantage and implemented a clear-and-hold strategy aimed at moving into rural enclaves formerly dominated by the VC."
Much criticized for lack of precision, the Phoenix Program was described by a former official as a "sterile depersonalized murder program...I never knew an individual to be detained as a VC suspect who ever lived through an interrogation"
One of the many problems with Phoenix is that it measured progress using metrics that were both deficient in value in predicting counterinsurgent success, but also provided incentives for undesirable actions that alienated the population. Evaluators of the Phoenix program confused "measures of effectiveness (MOEs) and measures of performance (MOPs)." MOPs evaluate how well an organization executes an action, but does not judge how well the action contributes to long-term results, which is the role of a MOE.
The Phoenix program used the MOP of "numbers of neutralization" by killing or capturing suspected VCI as a MOE, which was strategically unsound, especially when the higher command levels set body counts and captured counts as quotas. The objective of Phoenix was "to limit the VCI’s ability to support operations and exercise control over the population. Neutralization numbers did not measure whether Phoenix was effective."
Further, the quotas bred corruption, variously encouraging the denunciation of people as suspected VCI and "neutralizing" such people, without making it clear the denunciation was other than settling a grudge. Even when the suspect was detained rather than killed, they might be jailed for long periods before being cleared -- and those jails were excellent recruiting grounds for real VC to appeal to the anger of unjustly detained people.
- Friedman, Herbert A., The Phoenix Program
- Andrade, Dale & James H. Willbanks (March/April 2006), "CORDS/Phoenix: Counterinsurgency Lessons from Vietnam for the Future", Military Review
- COMMITTEE ON GOVERNMENT OPERATIONS HOUSE OF REPRESENTATIVES - U.S. Assistance Programs in Vietnam - Statement of K. Barton Osborn (2 August 1971).
- Ken Tovo (18 March 2005), From the Ashes of the Phoenix Lessons for Contemporary Counterinsurgency Operations, United States Army War College