Peter Jacksons WWI documentary "They Shall Not Grow Old" pays homage to the resilience of soldiers in WWI, while showing the horror of war. The restored footage is intimate and breathtaking- and is brought even more to life, with commentary from WWI soldiers/veterans that was compiled from hours of BBC interviews.
My understanding is the theatrical run was limited. In any event, if you can manage see it, stick around for the fascinating "special features" at the end.
NY TIMES - How Peter Jackson Made WWI Footage Seem Astonishingly New With ‘They Shall Not Grow Old’