But it's more a documentary - not necessarily a movie with a plot.
Directed by Peter Jackson - who directed the Lord of the Rings trilogy. Dude collected a bunch of uniforms and things.
They do an excellent job of taking old film and even colorizing and adding sound to the film. This includes using lip readers to know what people were saying on old film that didn't have sound and then using voice actors to add the sound in. There's film and photos of real dead people - so not for the feint of heart (not that Saving Private Ryan is free of death and destruction).
I watched this in the theater with my daughter - who teaches history. It was an awesome film and gave a tone of insights into WWI, taken primarily from the British perspective. It includes voice from recordings of actual WWI soldiers that they use to narrate throughout.
If you want to watch a film about WWI that will keep your interest but doesn't necessarily tell the story of one person, etc., I highly recommend this film. Very very well done.