They Shall Not Grow Old will be released in theaters as a Fathom Event on December 17th and December 27th. It will expand to NY/LA/DC on 1/11/19 followed by additional cities.
Back in 2014, just when he was wrapping production on the third of his Hobbit movies, Peter Jackson was approached by the British Imperial War Museum and the BBC about making a documentary film to commemorate British soldiers upon the 2018 centennial of World War I’s Armistice Day. Jackson was granted access to century-old footage from the museum’s archive, as well as old BBC audio interviews with some of the soldiers who actually fought in the war. Jackson was explicitly instructed to use this footage to tell the soldiers’ story.
Source: IGN.com Peter Jackson's They Shall Not Grow Old Review