I don't think it is based on a true story.
Good war movies by war:
World War Two: The Thin Red Line (1998 version)
Korean War: M*A*S*H (set in Korea but it's really about Vietnam)
Vietnam War: Lot's of good ones, the best is probably Apocalypse Now (the extended Redux version), also Good Morning Vietnam, Born On The 4th Of July and Full Metal Jacket.
Although Saving Private Ryan gets all the publicity, The Thin Red Line has much more realistic battle scenes, and more fully captures the horrors of war.
I can't think of any good 1st World War movies, but any that come along will be completely outshined by the TV comedy series "Blackadder Goes Forth"