Andrew Garfield in Hacksaw Ridge.

Mel Gibson has directed his first movie in a decade—and it bleeds. It bleeds a lot.

As a director, Gibson stands alongside the likes of Sam Raimi, David Cronenberg and Peter Jackson as a master of bloody horror. In fact, his latest, Hacksaw Ridge, is an all-out horror film in parts. His depiction of World War II makes George Romero’s Dawn of the Dead look like Zootopia.

The movie tells the true story of Desmond Doss (Andrew Garfield), a battlefield medic and the first conscientious objector in American warfare history to receive the Medal of Honor. The dude refused to pick up a gun—or any weapon, for that matter—during his time served in Okinawa. That didn’t stop him from braving the battlefields with comrades, eventually saving the lives of 75 men during horrendously bloody battles.

Much of the film’s first half is devoted to Doss’ backstory, including a troubled childhood with his alcoholic World War I-veteran father (a good Hugo Weaving) and a romance with future wife Dorothy Schutte (Teresa Palmer). The early goings-on in the film are handled well, although they are a little schmaltzy at times. Gibson isn’t at his best when he’s handling the romance stuff.

When Doss goes to boot camp and faces off against commanding officers like Capt. Glover (Sam Worthington) and Sgt. Howell (Vince Vaughn), the film starts to get very interesting. Due to his Seventh-day Adventist beliefs, Doss refuses to pick up a rifle, and this gets him into all sorts of trouble on the training field and in the barracks. After a detour for a court-martial hearing, Doss and his infantry mates are deployed to Japan.

When the action switches to the scaling of the Maeda Escarpment—aka Hacksaw Ridge—the film becomes perhaps the most grueling war-movie experience ever. Gibson, as he’s proven before with Braveheart, The Passion of the Christ (aka When Jesus Got His Ass Kicked) and Apocalypto, doesn’t shy away from movie violence, and this one is a major splatter fest. Hacksaw Ridge is honorable and majestic in its treatment of Doss, for the most part, but it’s not the easiest film in the world to watch. I saw the film as part of a matinee crowd filled with many folks who were alive at the time of Doss’ actual feats—and I’ve never heard so many screams and audible expressions of discomfort in a movie screening before. Frankly, I’m surprised Hacksaw Ridge didn’t get an NC-17 rating.

Garfield does his best screen work to date as Doss (he even physically resembles him), a man who deserves the almost saint-like portrayal he gets in this movie. Garfield is the total embodiment of goodness here, and he pulls off every moment he spends onscreen, including the corny ones. Vince Vaughn has dabbled in dramatic departures from his usual comedies before, but never as effectively as he does here as a drill sergeant who can’t believe what he’s seeing and hearing in regards to Doss.

Sam Worthington also does career-best work as Capt. Glover, portrayed in the film as Doss’ biggest foe within the military—until they share a battlefield together. Palmer gets a real chance to show her star power, and she capitalizes on that chance while also delivering a career-best performance.

It’s a testament to Gibson’s powers as a director that he gets a lot of career-best performances out of his cast. As for his staging of the battle scenes, they aren’t just bloody: They are absolutely terrifying. Gibson is trying to get across the message that Doss and his fellow soldiers went through the very worst hell on Earth—and he succeeds in a colossal way.

Yes, Gibson is a full-blown nut—and, as it turns out, he’s the perfect director to tell this amazing story. Hacksaw Ridge isn’t a total masterpiece, but it has passages that qualify it as one of the more essential war films ever made. Not bad for a guy who took a 10-year break from the director’s chair after … well, you know.

Hacksaw Ridge is playing at theaters across the valley.