His first credited role was in Ford's "3 Godfathers"; the film is notable for the riding skills demonstrated by both Johnson and star Pedro Armendáriz. He later said the film was the most physically challenging of his career. Ford then suggested a starring role for him in the 1949 film "Mighty Joe Young"; he played "Gregg" opposite Terry Moore. Ford cast him in two of the three films that have come to be known as Ford's cavalry trilogy, all starring John Wayne: "She Wore a Yellow Ribbon" (1949), and "Rio Grande" (1950); both roles showcased Johnson's riding ability. Ford also cast Johnson as the lead in "Wagon Master" (1950), one of Ford's favorites.