Heroin addiction in soldiers in Vietnam was overcome by removing them from environmental cues that prompted their addiction.

“it was the surprise that we saw from the Vietnam War which is so many soldiers were getting addicted to heroin and drugs when they were over there and then they came back and we were like what are we going to do with all these addicted soldiers and it turns out that 90% of them or more uh ended up being fine because they didn't go back to the place where they got addicted they went home to their friends and family and like they didn't have all the same signals uh that were prompting them to pick up the habit and so they were able to drop it much more easily than we thought they would”