The United States ran an extensive program of psychological warfare during the Vietnam War. The Phoenix Program had the dual aim of assassinating National Liberation Front of South Vietnam (NLF or Viet Cong) personnel and terrorizing any potential sympathizers or passive supporters. Chieu Hoi program of the South Vietnam government promoted NLF defections.
When members of the PRG were assassinated, CIA and Special Forces operatives placed playing cards in the mouth of the deceased as a calling card. During the Phoenix Program, over 19,000 NLF supporters were killed. The United States also used tapes of distorted human sounds and played them during the night making the Vietnamese soldiers think that the dead were back for revenge.
The Phoenix Program (Vietnamese: Chiến dịch Phụng Hoàng) was a program designed and coordinated by the United States Central Intelligence Agency (CIA) during the Vietnam War, involving cooperation between American, South Vietnamese and Australian militaries.
The program was designed to identify and destroy the Viet Cong (VC) via infiltration, torture, capture, counter-terrorism, interrogation, and assassination. The CIA described it as "a set of programs that sought to attack and destroy the political infrastructure of the Viet Cong". The Phoenix Program was premised on the idea that infiltration had required local support from non-combat civilian populations, whom was referred to as the "political branch" whom coordinated the insurgency including propaganda, recruitment and assassination of South Vietnamese officials and others associated with the government.
Throughout the program, Phoenix "neutralized" 81,740 people suspected of VC membership, of whom 26,369 were killed and the rest surrendered or were captured. A number of criticisms arose regarding the Phoenix Program, including the unknown number of neutral civilians killed, the nature of the program (which critics have labelled as a "civilian assassination program"), the use of torture and other coercive methods, and the program being exploited for personal politics. Nevertheless, the program was described as suppressing Viet Cong political and revolutionary activities. Disclosure of the program publicly had caused significant criticisms, including congressional hearings, and the CIA was pressured to shut-down the Phoenix Program, although a similar program "Plan F-6" continued under South Vietnamese authorities.