In 2015, a year into the First World War centenary, the arts program 14-18 NOW had an idea: Commission a film, in concert with the Imperial War Museum and the BBC, comprising 600 hours of interviews with WWI vets and 100 hours of footage preserved by the museum. The group had one man in mind for the job: Peter Jackson, he of The Lord of the Rings and The Hobbit, Meet the Feebles and Bad Taste, last seen loaning his name to promote Christian Rivers’ Mortal Engines.

Jackson accepted the assignment, but ran into an immediate problem: turning all of that footage into an actual documentary. Even with such profound, ground-level material at his disposal, he needed to distinguish his film from existing works like Gallipoli, The Millionaire’s Unit, and 25 April. Unsurprisingly, Jackson rang Weta Digital, the visual-effects outfit he founded in 1993 with Richard Taylor and Jamie Selkirk, with a big idea to set his movie, They Shall Not Grow Old, apart from its cousins.

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Actually, three ideas: First, Jackson restored the footage gifted to him by the Imperial War Museum — not just the footage he ended up using in the film, but all 100 hours. Second, he colorized the footage he used in the film to make it more lifelike. And third, he barred voice-over narration from the film — if anyone was going to be heard, it would be a primary source. They Shall Not Grow Old would forgo as much third-party interpretation as possible to let the words of the men who risked their lives in global conflict tell their own story. Save for the astounding restorative efforts, Jackson, a filmmaker of distinct contemporary instincts, rejects contemporary perspective in telling their stories.

“I gave every part of my youth to do a job,” declares one soldier in the opening of They Shall Not Grow Old. His sentiment reverberates throughout: Like miners to headframes, fishermen to oceans, and lawyers to courtrooms, English troops bade farewell to their home as any working man would. The difference is that most didn’t come back at the end of the day. That’s what one does in service to queen and country. “Get on and do it,” another voice insists over images of men marching off to battle, a prototypically British way of looking at a task as monumental as putting one’s life on the line, as if starving in festering trenches smack dab in no man’s land while dodging shrapnel and bullets isn’t a big ask.

“There’s work needs doing. Strap on your helmet. Pull up your britches. Get on the boat. Bob’s your uncle, pip pip.”

As the film moves forward, another attitude emerges from the chorus of testimonials: that if these chaps could do it all again, they wouldn’t change a thing, as if missing out on such a grueling experience would have left them with a lifetime of regret. At points, the soldiers sound like they’re talking about summer camp instead of global warfare. It’s all talk and bluster, of course; later, long after Jackson transitions from black and white to startling color, the picture smash-cuts from a shot of smiling English faces to a gory pile of corpses, a harsh reminder of WWI’s brutal realities. The camaraderie is real, but so is the danger.

A sense of camaraderie and danger connects They Shall Not Grow Old with the most ambitious films of Jackson’s oeuvre. Sandwiched between his recent work and the splattery DIY horror movies of his 20s were the Lord of the Rings movies, the epic trilogy that demonstrated the best of him as an an innovator and an unexpected humanist. The films are special-effects marvels, big productions built on little solutions for tackling the scale of Tolkien’s texts, but they endure 16 years later because of their abiding compassion. The films’ thrills are found in titanic battle sequences, but their souls are couched in quiet moments: a lesson in swordcraft for two hobbit chums, a drinking contest between friendly rivals, a disagreement over how best to prepare a brace of coneys. Even brief beats affording awesome views of oliphants contain more wonder than the great onslaughts capping The Return of the King.

They Shall Not Grow Old, a title layered with literal and figurative meaning, finds family resemblance in the spirit of Jackson’s best work. The director’s reputation has fallen off since the early 2000s, first with King Kong, then The Lovely Bones, and last but not least his choice to split The Hobbit into three movies tonally ill-suited to their source.

But They Shall Not Grow Old asserts Jackson’s vitality as an artist and as an advocate for his medium. The men who gave their lives during World War I forsook the privilege of growing older. In Jackson’s film, they’ll keep their youth, vigor, and bravery forever.

They Shall Not Grow Old is out now in select theaters.