I just saw the new "Lincoln" movie yesterday, and there is a scene where, after the thirteenth amendment has passed the House of Representatives, the pro-amendment congressmen start singing "The Battle Cry of Freedom". I had always understood that this song was written by George Frederick Root, but in the movie credits it is listed as "Traditional".

Is this a case where the persons responsible for the movie credits simply didn't do their homework? Or is there a contention (of which I am not aware) that Root simply signed his name to an existing traditional song? Or maybe Root wrote the words, but the tune is traditional?

Don