Director Mel Gibson’s Hacksaw Ridge is not a subtle enterprise. Based on a true story, this war drama starts off as an unabashedly earnest coming-of-age tale before shifting into a harrowing, blood-and-guts battlefield saga. There’s power in Gibson’s simplicity and hardheaded certainty, and there are moments in his film so utterly absorbing that quibbles about the lack of character nuance feel entirely beside the point. And yet, the kind of heroism that Gibson champions ultimately feels too one-dimensional. In a world full of complexity, he insists on seeing everything in black-and-white.

The movie chronicles the life of Desmond Doss (Andrew Garfield), a Virginian who fought in the Pacific during World War II. A devoutly religious young man, Doss volunteered for military service because he loved his country, but his strict refusal to kill put him at odds with his commanding officers, who insisted he was going to have to learn how to fire a gun.

That conflict serves as Hacksaw Ridge’s central drama in its first half, and Andrew Garfield is quietly great as Doss, making virtue feel endearingly noble. Falling in love with a local nurse, Dorothy (Teresa Palmer), Doss is a sweet, slightly goofy guy—he’s so uncynical you keep thinking it’s an act. Gibson stages these early scenes as if he’s filming an old-fashioned romantic drama. (It’s the first time since his directorial debut, 1993’s The Man Without a Face, that he’s embraced such homespun sentimentality.) Doss and Dorothy could almost be an advertisement for American decency, a throwback to an era in which the country fought in a war whose rationale was unquestionably just and we were clearly the good guys.

When the film shifts to basic training, the setup isn’t that different from Full Metal Jacket—here, Vince Vaughn plays the bullying, sarcastic sergeant—and soon Doss is running afoul of those around him, arguing that he wants to serve as an Army medic on the front lines. He’d rather save lives than take them. Doss is beaten and ridiculed by his fellow soldiers, and his superiors threaten to court-martial him, but he won’t budge, believing that he has to obey God’s law, not man’s.

Robert Schenkkan and Andrew Knight’s screenplay makes the most of this drama, playing into the familiar but potent allure of watching one principled man stand up to the system. We usually see this conflict in prison films—can our hero hold onto his core beliefs without having his spirit broken?—and Garfield turns Doss’ righteous stand into a humble, resilient protest. But in the process, the talented young actor (who’s been terrific in everything from Boy A to The Social Network) starts to create an interesting, and perhaps unintentional, conflict with his director. Gibson wants to deify Doss, but Garfield prefers to keep the character’s feet firmly planted on the ground.

Hacksaw Ridge’s square-jawed, cornball storytelling seems to be a reflection of Doss’ unfussy sincerity—the film’s first half is a paean to virtue and integrity—but it also helps Gibson more effectively blindside us when he moves to Japan for the film’s second half. If Hacksaw Ridge initially plays like a polished tribute to a remarkable but forgotten soldier—dying in 2006 at the age of 87, Doss was a Medal of Honor recipient—then the movie’s battle scenes feel even more brutal in contrast.

Ever since Steven Spielberg’s recreation of the storming of Omaha Beach, the opening of Saving Private Ryan has been held up as the high bar for all war films to follow. The startling rawness of that sequence—the pure shock of its execution—perhaps can never be matched, only duplicated, but Gibson gives us battle scenes that come close in their savagery, horror, and utter brilliance. This is not exactly new terrain for the man behind Braveheart and Apocalypto, but Gibson’s first film in ten years reminds us of his unique talent for unleashing hell. Doss’s regiment tries to take the titular ridge, even though they’re badly outnumbered by Japanese forces, and the filmmaker methodically watches as American soldiers fight their way to better strategic positions, accruing massive, bloody casualties along the way. All the while, the unarmed Doss darts around the battlefield patching up his buddies while trying not to get killed.

As with all Gibson’s movies, Hacksaw Ridge’s best moments are the ones where conscious thought gives way to pure, visceral sensation. As a storyteller, he’s incredibly simplistic—a lone, morally upstanding individual is always outnumbered by vicious, wicked legions—but when he works through this theme in violent clashes, his films come to life in primal, sometimes slightly mad, ways. That’s especially true in Hacksaw Ridge’s battle sequences. I can’t say I learned anything new about Doss or his fellow soldiers in those scenes, but the sheer pummeling of gunfire, explosions, and shattered limbs compelled me to sympathize with them in a way that earlier scenes never could. On a technical level, the Japanese set pieces are extraordinary—not just graphic but also brilliantly staged and executed, always giving us a clear sense of the geography and the back-and-forth struggle to claim the terrain for each side’s military.

Even here, though, Gibson never really expands his worldview, never allows a more intriguing, conflicting viewpoint to have its say. Not surprisingly, the Japanese are portrayed as uniformly evil, and even Doss’ fellow soldiers are generic war-movie types. Nobody in Hacksaw Ridge is worth knowing other than Doss as far as Gibson is concerned.

But then again, Gibson only seems interested in Doss for the positive attributes he can lionize in him. With death all around him on Hacksaw Ridge, Doss (who had been labeled a coward at boot camp for his pacifism) shows the depth of his bravery, rescuing wounded soldiers and staging a courageous one-man campaign to get many of his countrymen to safety, even after the U.S. has lost the ridge. The real-life story is amazing, and Gibson provides suitable excitement to Doss’ climactic rescue mission, but as empathetic as Garfield is portraying a plainspoken guy who just wanted to do good for others, Hacksaw Ridge doesn’t really illuminate the man behind the heroism.

We see hints of a difficult childhood where Doss internalized the dangers of guns and violence, but virtue without some inner struggle starts to feel like simplemindedness rather than hard-fought principle. Gibson takes his protagonist’s belief system as a given, but you sense Garfield trying to add some gradation. Ultimately, Gibson wins the battle, but the far more interesting war gets away from him.

Grade: C+

Grierson & Leitch write about the movies regularly for the New Republic and host a podcast on film. Follow them on Twitter @griersonleitch or visit their site griersonleitch.com.