Try to find the movie, "Oh what a lovely war". It stars Lawrence Olivier, Dirk Bogard, and a host of others. Every song published ( and some not published) before the American entry into the war is in it. Including parodies that were frowned on by the higher ups. such as this parody of "Onward Christian Soldiers"

Onward British Soldiers, marching with your gear
While our bold commander is safely in the rear.
Hear him as he boasts about deeds so bold and brave
While the men who really did them are dead and in their graves.
Onward British soldiers, marching with their gear
While the Brave Commander is safely in the rear.

One sequence is about the first Christmas of the war when the German and British soldiers met in "no man's land", shook hands, exchanged gifts, drank toasts and returned to their respective trenches. This seq