The Philippines became self-governing in 1935, but their former colonizer the United States didn't recognize that until 1946. After World War II, the nations remained allies, but a communist insurgent group called Hukbong Bayan Laban sa Hapon, or Hukbalahap (Huk for short), who formed to fight the Japanese, fought for control of the Philippines.
The Americans appointed Lieutenant Colonel Edward Lansdale of the CIA to conduct operations against the Huks, which included psychological warfare. Lansdalen was charged with clearing one area of Huks in order to protect withdrawing American troops and their sympathizers, so he leveraged the legend of the aswang, a shapeshifting, human-animal hybrid vampire. This involved seeding the area with rumors of a curse and the threat of a vampire attack to come. The operation culminated in a staged vampire attack, complete with puncture holes in the victim's neck! Read how they pulled that off, and what happened afterward, at Mental Floss.
(Image credit: Scary Side of Earth)