Hawks saw cattleman potential in Clift, and wisely advised him to display Matt's strength through arrogant silence and airy coolness (he's constantly chewing wheat, rubbing his nose thoughtfully, and gazing into the Chisholm Trail distance offscreen). It was Hawks' wife Slim (having an affair with Clift's agent at the time) who convinced the hesitant actor to take the role.
Though Wayne considered Clift an "arrogant little bastard" and "a little queer," a three-week cram session in Arizona helped Montgomery become a convincing cowboy. An early can-shooting contest between Matt and Cherry Valance (John Ireland) also establishes his skill, though it's more celebrated for its hints at homoeroticism ("I've taken a liking to that gun of his") and the womanizing actor Ireland's reputed anatomical gifts ("Maybe you'd like to see mine"). Hawks carefully choreographed the climactic Duke vs. Monty brawl to make it believably even, saying he wore out his arm teaching Clift how to punch. For its reliable redneck supporting players (Walter Brennan, Hank Worden, Harry Carey), epic black and white vistas shot by Russell Harlan (The Big Sky, Rio Bravo), risk-taking (albeit heavily rinsed by Joseph Breen) screenplay, and fraught dynamic between its leads, Red River's top-shelf Western status is justly calcified.
Red River plays at BAM tonight as part of the That's Montgomery Clift, Honey! series.