Sir Sam Mendes (director) and Lee Smith (editor) stated that, despite the apparently continuous shot (broken only by one interval of unconsciousness), actually dozens of "invisible" edits were made, concealed by transitions through black, moves behind objects, and so on. According to Mendes, the shortest unbroken shot was 39 seconds long, while the longest single continuous shot was 8-1/2 minutes long.
It took six months for the actors to rehearse the movie before shooting started.
Inspired by Sir Sam Mendes' grandfather's experiences in WWI: "The Autobiography of Alfred H. Mendes 1897--1991."
Over 5,200 feet (1,584 meters) of trenches (just under 1 mile) were dug for the film.
Sir Sam Mendes says his grandfather Alfred, who entered WWI as a 17-year-old in 1916, carried messages through no-man's land. He was 5'4" tall and was often hidden by the winter mist that reached as high as 6 feet. Two years in the muddy trenches left Alfred with a lifelong habit of washing his hands frequently. He didn't talk about his wartime experiences until he was in his 70s.