Anyone who sees this 1971 film know the premise before hand: a soldier is wounded in during a battle in WWI, and is reduced to a limbless, faceless figure that is being kept alive in an army hospital—for reasons. Despite that, this is a completely bloodless, gore-less film, filled with performances, not graphic scenes. But try to watch this segments where the patient discovers what happened to him. Then consider how modern horror measures up to that.
The ending is a horror. Joe realizes he isn't going to be granted a merciful death, and will remain in his state until his natural death. As he drifts off, he can only tap SOS in morse code, but nobody will listen. A cruel fate to endure, and Joe has to undergo it after a hope spot of a possible death had been taken from him.
Joe's monologue at the end of the book, demanding that he be publicly displayed to demonstrate the true toll of war. It involves him asking to be brought into classrooms, knowing that children will cry and get nightmares from seeing him, and asking young women to kiss the wound where his face used to be.
