There is a story that the head of the studio that made this film wanted to pull the plug on it because he thought it subversive.
He was right. It subverts a number of genres: it is a western without any horses; a war story thousands of miles from the front line; a thriller like a ghost story; a film noir set in the desert. But most subversive of all, at the core of the film it is about the consequences of racism, most specifically anti-Japanese racism, and how that racism is often dressed up as patriotism.
The film takes the form, popular in US and Japanese cinema, of the stranger arriving into town as a catalyst for the unfolding story. Spencer Tracy delivers one of his most iconic performances as the stranger, a brave man, but one who has seen too much violence already not to appreciate that, when faced with insurmountable odds, discretion is the better part of valour. Robert Ryan is brilliantly terrifying as the charming thug who dominates the town. Walter Brennan provides some light relief as the town undertaker and vet in the midst of a spare and nightmarish story.
The film must still be regarded as deeply subversive to those "heartland" Americans for whom ignorance and provincialism are regarded as virtues. The outsider played by Tracy asserts a different sort of Americanism, a cosmopolitan, progressive and principled one, and is hated and feared as a result.
For Trivial Pursuit and pub quiz afficianados: the film is said to be the first American film to portray the use of eastern martial arts when Tracy's character comes to a point at which he is driven to fight in self-defense, and displays a surprising propensity for karate, the Japanese martial art.