 Montgomery Clift (qv) threw himself into the character of Prewitt,  learning to play the bugle (even though he knew hed be dubbed) and  taking boxing lessons. Fred Zinnemann (qv) said, "Clift forced the  other actors to be much better than they really were. Thats the  only way I can put it. He got performances from the other actors, he  got reactions from the other actors that were totally genuine."