There was a squad of soldiers in the jungles of Vietnam. They were all setting up a site to sleep at during the night. The radio had absolutely no signal coming in. They completely were on their own.
During the night, the watchman was watching for enemy soldiers. He had kept hearing strange noises, but dismissed them as jungle animals.
There was something he could see in the distance, but had no idea what to think of it.
He saw some very strange writing that looked like it was in some foreign language, but he didn't understand what the language might be. He decided to go investigate.
He pulled out a book that could translate Vietnamese into English.
The message on the wall said something along the lines of this: "He must never be awakened, for he will bring about absolute destruction to even those who worship him."
The soldier thought nothing of it. He decided to look around the wall. He saw English writing on the side of the wall: "R'yaleigh is hell."
The soldier had read Lovecraftian writings before such as The Call Of Cthulhu, but had thought it was fantasy.
He suddenly tripped on something, and fell into the wall. The wall broke, leaving a hole in it.
The soldier then saw the staircase, which he tumbled down...
A new squad of soldiers came upon many dead soldiers, one of them had built an altar and had sacrificed the rest of them.
He kept mumbling something about the great old ones, while blood filled his mouth. He praised the great old ones until his death three months later.
He had slit his throat with a hospital needle. He left a suicide note which read: "My fellow humans, a terrible evil lives under the earths surface in the city of R'yaleigh, and I have escaped this evil. You must do what I have done before its too late Praise the Great Old Ones."