The Big Parade (1925)

In the period before The Great War, James Apperson lives a good life thanks in large part to his father's fortune. He's engaged to the beautiful Justyn Reed. He's something of a disappointment to his father; thankfully, his more-serious brother plays the good son and is involved in the family business. When the U.S. enters the the war, James is caught up in all the hoopla and enlists. He makes new friends, particularly Slim and Bull, and they're soon off to France. While awaiting their move to the front lines, James meets young Frenchwoman Melisande. Life is good for all of them, but when they move up, they experience the horrors of war and James is forever a changed man.

IMDb: https://www.imdb.com/title/tt0015624