The Big Red One isn't so much a war movie as it is a message, sometimes obscure, of what war is really like. There is much symbolism in this movie, for example the human arm, with a wristwatch on it, washing in the bloody surf of Omaha Beach. If you want realistic detail of combat, watch Saving Private Ryan. If you want to the voice of experience, blurry from the passage of time, The Big Red One is a movie to see.
Keep in mind that this movie reflects the life experiences of some survivors of WWII. That Lee Marvin was cast as the grizzled sergeant is part of the symbolism: Marvin was a combat Marine who participated in the invasion of Saipan; he is cast as a survivor of WWI who is retracing part of the path he took during that conflict. I found some of the scenes from the movie barely believable, for example, the French insane asylum, but you must keep in mind that there is a message from the survivors of that war in each and every scene. How you take the message, apparently, is up to you.
Keep in mind that this movie reflects the life experiences of some survivors of WWII. That Lee Marvin was cast as the grizzled sergeant is part of the symbolism: Marvin was a combat Marine who participated in the invasion of Saipan; he is cast as a survivor of WWI who is retracing part of the path he took during that conflict. I found some of the scenes from the movie barely believable, for example, the French insane asylum, but you must keep in mind that there is a message from the survivors of that war in each and every scene. How you take the message, apparently, is up to you.