Great role for Bronson.
Compare Bronson's fighting style with almost any other fight movie like Kirk Douglas in 'Champion' or Stallone in the 'Rocky' series. Bronson slips and ducks his opponent's punches like a real fighter does, putting as much effort into not getting hit as he does hitting the other guy. Any fighter taking the hits that most movie boxers take would be unconscious or dead in a matter of minutes, and even sluggers like Rocky Marciano and George Frazier were constantly moving, never offering a good target.
This depression era movie is similar in flavor to the Lee Marvin Ernest Borgnine vehicle 'Emperor of The North'. Both movies have unsentimental, tough, taciturn heroes who communicate more with glances and gestures.