Vietnam.

We called the enemy ghosts. "Bad night," we'd say, "the ghosts are out." To get spooked, in the lingo, meant not only to get scared but to get killed. "Don't get spooked," we'd say. "Stay cool, stay alive." Or we'd say: "Careful, man, don't give up the ghost." The countryside itself seemed spooky-- shadows and tunnels and incense burning in the dark. The land was haunted. We were fighting forces that did not obey the laws of twentieth-century science. Late at night, on guard, it seemed that all of Vietnam was alive and shimmering-- odd shapes swaying in the paddies, boogiemen in sandals, spirits dancing in old pagodas. It was ghost country, and Charlie Cong was the main ghost. The way he came out at night. How you never really saw him, just thought you did. Almost magical--appearing, disappearing. He could blend with the land, changing form, becoming trees and grass. He could levitate. He could fly. He could pass through barbed wire and melt away like ice and creep up on you without sound or footsteps. He was scary. In the daylight, maybe, you didn't believe in the stuff. You laughed it off. You made jokes. But at night, you turned into a believer; no skeptics in foxholes.

"The Things They Carried" - Tim O'Brien