Mel Gibson’s “Hacksaw Ridge” is a brutally effective, bristlingly idiosyncratic combat saga — the true story of a man of peace caught up in the inferno of World War II. It’s the first movie Gibson has directed since “Apocalypto,” 10 years ago (a film he’d already shot before the scandals that engulfed him), and this November, when it opens with a good chance of becoming a player during awards season, it will likely prove to be the first film in a decade that can mark his re-entry into the heart of the industry. Yet to say that “Hacksaw Ridge” finally leaves the Gibson scandals behind isn’t quite right; it has been made in their shadow. On some not-so-hard-to-read level, the film is conceived and presented as an act of atonement.

It should be obvious by now that the question of whether we can separate a popular actor or filmmaker’s off-screen life from his on-screen art doesn’t have a one-size-fits-all answer. Every instance is different. In the case of Mel Gibson, what we saw a number of years ago — first in his anti-Semitic comments, then in leaked recordings of his phone conversations — wasn’t simply “objectionable” thoughts, but a rage that suggested he had a temperament of emotional violence. It was one that reverberated through his two most prominent films as a director: “The Passion of the Christ,” a sensational and, in many quarters, unfairly disdained religious psychodrama that was a serious attempt to grapple with the stakes of Christ’s sacrifice, and “Apocalypto,” a fanciful but mesmerizing Mayan adventure steeped to the bone in the ambiguous allure of blood and death.

Like those two movies, “Hacksaw Ridge” is the work of a director possessed by the reality of violence as an unholy yet unavoidable truth. The film takes its title from a patch of battleground on the Japanese island of Okinawa, at the top of a 100-foot cliff, that’s all mud and branches and bunkers and foxholes, and where the fight, when it arrives (one hour into the movie), is a gruesome cataclysm of terror. Against the nonstop clatter of machine-gun fire, bombs and grenades explode with a relentless random force, blowing off limbs and blasting bodies in two, and fire is everywhere, erupting from the explosions and the tips of flame-throwers. Bullets rip through helmets and chests, and half-dead soldiers sprawl on the ground, their guts hanging out like hamburger.

Yet at the center of this modern hell of machine-tooled chaos and pain, there is Desmond Doss (Andrew Garfield), a soldier who refuses to carry a gun because it is against his values. He’s a conscientious objector who acts as a medic. But because he’s every bit as devoted to serving in the war as he is to never once firing a bullet, he isn’t just caring for soldiers. He’s on the front lines, in the thick of the thick of it, without a weapon to protect him, and the film exalts not just his courage but his whole withdrawal from violence.

There really was a Desmond Doss, and the film sticks close to the facts of his story. Yet there’s still something very programmatic about “Hacksaw Ridge.” It immerses you in the violent madness of war — and, at the same time, it roots its drama in the impeccable valor of a man who, by his own grace, refuses to have anything to do with war. You could argue that Gibson, as a filmmaker, is having his bloody cake and eating it too, but the less cynical (and more accurate) way to put it might be that “Hacksaw Ridge” is a ritual of renunciation. The film stands on its own (if you’d never heard of Mel Gibson, it would work just fine), yet there’s no point in denying that it also works on the level of Gibsonian optics — that it speaks, on some political-metaphorical level, to the troubles that have defined him and that he’s now making a bid to transcend.

Will audiences, and the powers of Hollywood, finally meet him halfway? One reason the likely answer is “yes” is that “Hacksaw Ridge,” unlike such landmarks of combat cinema as “Saving Private Ryan,” “Platoon,” or “Full Metal Jacket,” isn’t simply a devastating war film. It is also a carefully carpentered drama of moral struggle that, for its first hour, feels like it could have been made in the 1950s. It’s a movie that spells out its themes with a kind of homespun user-friendly clarity. We see Desmond as a boy, growing up in a small town on the edge of the Blue Ridge Mountains of Virginia with a drunken abusive father (Hugo Weaving) and a mother (Rachel Griffiths) he’s driven to protect. Early on, Desmond gets into a fight with his brother and hits him in the head with a brick, and that incident, which leaves him reeling in sorrow, is the film’s version of one of those “Freudian” events that, in an old Hollywood movie, form the cornerstone of a person’s character.

It all seems a bit pat, but once Desmond grows up and Andrew Garfield starts playing him, the actor, all lanky charm and aw-shucks modesty, wins us over to seeing Desmond as country boy of captivating conviction. He knows nothing about girls, yet he woos a lovely local nurse (Teresa Palmer) with a fumbling sincerity that melts her resistance. And when the war arrives, he enlists, just like his brother, because he feels he has no choice not to. He’s a Seventh Day Adventist scarred by violence in his family; all of this plays a role in his pacifism, and his patriotism. That difficult dad of his is portrayed by Hugo Weaving as a haunted, complex man: a slovenly lush who tries to keep his family in line with the belt, and even the pistol, but also a decorated veteran of World War I who is desperate to keep his sons alive.

The film revs up its old-fashioned pulse when it lands at boot camp, where Desmond proves a contradiction that no one there — not his fellow soldiers, let alone the officers — can begin to fathom. He’s an eager, good-guy recruit who refuses to pick up a rifle even for target practice; they assume (wrongly) that he must be a coward. For a while, the film is strikingly reminiscent of the legendary Parris Island boot-camp sequence in “Full Metal Jacket,” only this is WWII, so it’s less nihilistic, with Vince Vaughn, as the drill sergeant, tossing off the wholesome version of the usual hazing insult zingers; he looks at Desmond and barks, “I have seen stalks of corn with better physiques.” (Hence Desmond’s Army nickname: Cornstalk.) “Hacksaw Ridge” often feels like an old studio-system platoon movie, but when Desmond’s pacifism becomes a political issue within the Army, it turns into a turbulent ethical melodrama — one can almost imagine it as a military courtroom drama directed by Otto Preminger and starring Montgomery Clift.

The question is whether the Army will allow Desmond, on his own terms, to remain a soldier — a conscientious objector who nevertheless wants to go to war. In a sense, the dramatic issue is a tad hazy, since Desmond announces, from the outset, that he wants to be a medic. Why can’t he just become one? But one of the strengths of “Hacksaw Ridge” is that it never caricatures the military brass’s objections to his plan. On the battlefront without a weapon, Desmond could conceivably be placing his fellow soldiers in harm’s way. His desire is noble, but it doesn’t fit in with Army regulations (and the Army, of course, is all about regulations). So he’s threatened with a court martial. The way this is finally resolved is quietly moving, not to mention just.

And then … the hell of war. It’s 1945, and the soldiers from Desmond’s platoon join forces with other troops to take Hacksaw Ridge, a crucial stretch — it looks like a Japanese version of the land above Normandy beach — that can lead them, potentially, to a victory in Okinawa, and the beginning of the end of the war. Gibson’s staging of the horror of combat generates enough shock and awe to earn comparison to the famous opening sequence of “Saving Private Ryan,” although it must be said that he borrows a lot from (and never matches) Spielberg’s virtuosity. Yet Gibson creates a blistering cinematic battleground all his own. Each time the fight breaks out again, it’s so relentless that you wonder how anyone could survive it.

The real story that “Hacksaw Ridge” is telling, of course, is Desmond’s, and Gibson stages it in straightforward anecdotes of compassion under fire, though without necessarily finding anything revelatory in the sight of a courageous medic administering to his fellow soldiers (and, at certain points, even to wounded Japanese), tying their blown-off limbs with tourniquets, giving them shots of morphine between murmured words of hope, and dragging them to safety. In a sense, the real drama is a nobility that won’t speak its name: It’s the depth of Desmond’s fearlessness, and his love for his soldier brothers, which we believe in, thanks to Garfield’s reverent performance, but which doesn’t create a combat drama that’s either scary or exciting enough to rival the classic war movies of our time. This isn’t a great one; it’s just a good one (which is nothing to sneeze at).

Desmond devises a way to save lives by tying a rope around the soldiers’ bodies and lowering them down the vertical stone cliff that borders Hacksaw Ridge, and using that technique he rescues a great many of them. Desmond Doss, who saved 75 men at Hacksaw Ridge, became the first conscientious objector to receive the Medal of Honor, and Gibson has made a movie that’s a fitting tribute to him (at the end, he features touching footage of the real Doss). But one surprise, given the drama of pacifism-versus-war that the movie has set up, is that there’s never a single scene in which Desmond has to consider violating his principles and picking up a weapon in order to save himself or somebody else. A scene like that would have brought the two sides of “Hacksaw Ridge,” the violent and the pacifist — and, implicitly, the two sides of Mel Gibson — crashing together. But that would have been a different movie. One that, in the end, was a little less safe.