A couple of weeks ago, I named Peter Jackson’s “They Shall Not Grow Old” one of the Best Documentaries Of 2019. It showed the brutality of war through the experiences of the young men who were caught up in the middle of it.

Now comes Sam Mendes’ “1917,” based on stories he heard from his grandfather Alfred, who served in that war. Its plot is simple. Two British soldiers, Schofield (George MacKay) and Blake (Dean-Charles Chapman) are tasked with delivering a message to stop an attack on German troops who have seemingly retreated, but have really set a trap and are ready to ambush the Englishmen, possibly killing as many as 1,600 of them.

The movie then follows the two men as they traverse the French countryside on foot, through trenches and across muddy fields. As they do so, the camera stays with them, seemingly in one long take. That’s a movie trick that goes back to Alfred Hitchcock’s “Rope,” but updated with today’s much improved technology. Mendes and legendary cinematographer Roger Deakins put us right down at the soldiers’ level, sometimes showing their point of view, at others pulling back to let us see them, but never cutting away to show us what’s happening anywhere else. It’s as if we’re embedded with these two young protagonists as witness to the near-impossibility of their mission and the realities of war they encounter.

The result is nothing less than stunning.

Still, there were a few times when I was drawn out of the storyline by the mechanics of a shot to think, “How the hell did they do that?” For instance, there’s a scene in which the two soldiers have to cross a river on a bombed-out bridge, and the camera tracks them from the side, as if it’s gliding through the air across the water. It’s an impressive feat of movie-making, but a slight distraction.

Mendes is not the first to toy with the form of the war movie. Jackson did it by colorizing and animating 100-year-old footage of real scenes from World War I. Steven Spielberg showed the ferocity of the Normandy landing in the first 20 minutes of “Saving Private Ryan,” setting a new standard for how military action is depicted on screen. Christopher Nolan did it by making “Dunkirk” with three different but coinciding time lines.

Though there are big-name actors in “1917” — including Colin Firth at the beginning and Benedict Cumberbatch at the end — Mendes was smart to cast two unknowns as the young messengers. Thus, they come off as relatable Everymen, fighting their way through hell to save their fellow soldiers.

I give “1917” a 9 out of 10. It will be on my Best Movies of 2020 list.