As the Vietnam war dragged on, the US military began desperately searching for any vulnerability in their North Vietnamese enemy. In 1964, they found it. It was an old Vietnamese folktale involving a ghost, eternal damnation and fear - a tailor made weaponizable myth. And so, armed with tape recorders and microphones, the military set out to win the war by bringing this ghost story to life. Today, the story of these efforts and their ghosts that still haunt us today.  Mixtape is reported, produced, scored and sound designed by Simon Adler with original music throughout by Simon. Indispensable reporting and production assistance was provided by Eli Cohen. This episode was produced by Annie McEwen, with original music by Annie. Original reporting was contributed by Trung Dung Vo and Nguyễn Vân Hà. Special thanks to: Allison Boccia, Jared Tracy and Herb Friedman. And to Mathew Campbell for introducing me to the Wandering Soul tape to begin with. And to Erik Villard for all his help pulling those tapes and voices for us.  Support Radiolab by becoming a member today at Radiolab.org/donate.