Director and actor Mel Gibson on the red carpet for Hacksaw Ridge at the Venice Film Festival on September 4. Credit:AP Its rival magazine Variety described the film as "a brutally effective, bristlingly idiosyncratic combat saga" that was "a testament to (Gibson's) film-making chops and an act of atonement that may succeed in bringing him back." Clearly, his sins are not forgotten. "As repellent a figure as many may still find Gibson," wrote The Guardian's critic, "I have to report that he's absolutely hit Hacksaw Ridge out of the park." Hacksaw Ridge was mostly filmed in Australia last year, except for some shooting in Doss's home town of Virginia, with a largely Australian cast and crew. But it tells a very American story. Doss was a conscientious objector, but he enlisted in the US Army during World War II as a medic. His refusal to touch a weapon during training brought mockery, bullying and a court-martial for insubordination, but he stuck it out. He was then part of the force that attacked Hacksaw Ridge, a natural barrier protecting the Japanese stronghold of Okinawa. Casualties were heavy; wounded soldiers were everywhere. So were the Japanese, forcing the Americans to withdraw. Only Doss stayed and looked for wounded under cover of night, dragging them single-handed to the top of the cliff and lowering them down. In 10 hours he rescued 75 men, a feat that was seemingly superhuman. He was subsequently awarded the Medal of Honour in recognition of his bravery.

Mel Gibson's Hacksaw Ridge. Credit:Mark Rogers Gibson believes, as Doss did himself, that God gave him the strength to drag, haul and comfort those man. Doss, who died in 2006, was a devout Seventh-Day Adventist. "He's operating on something greater than himself. He's tapping into something supernatural to do something superhuman," says Gibson. "Nobody could understand how he did it. Dragging a dude every 10 minutes and lowering him … how do you even start with that? But he did it. And he was only 150 pounds wringing wet." It is 10 years since Gibson has sat in the director's chair; his last film was Apocalypto in 2006. It was not long after he finished shooting that film, which was in itself notable for the fact that the dialogue was in the ancient Mayan language, that he famously hurled anti-Semitic abuse at a police officer who had stopped him for drunk-driving. Four years later, a tape of Gibson delivering a drunken, racist tirade to his then-partner Oksana Grigorieva set the seal on his sullied reputation. "Sometimes you take a big step backwards," he tells the press conference that follows the Venice screening "I've done it." Hacksaw Ridge is clearly his chosen path to public redemption. Andrew Garfield as conscientious objector Desmond Doss in Hacksaw Ridge. For the first hour, the story is set in Doss's home town of Lynchburg, Virginia, where the Great Dividing Range stands in for the blue Virginia hills. Doss (played by English actor Andrew Garfield) joshes his brother, tries to mollify his drunken, erratically violent father – a First World War veteran clearly suffering from PTSD, played by Hugo Weaving – and courts a young nurse Dorothy, played by Australian actor Teresa Palmer. For Gibson, working in Australia felt "very familiar, like putting on a comfortable pair of shoes … it was fantastic to go back, catch up with people I went to school with. We're all wrinkled now. And apologise to everyone, you know!"

The final third of the film is largely set on the battlefield and is as graphically and horrifically violent and gory as the subject demands. "In Okinawa they used napalm for the first time," says Gibson. "And of course there were hand-grenades and mortars and explosions everywhere, so there was a lot of death. You just try to emulate what was – and there are devices now (for depicting that) that are pretty amazing." Mel Gibson with the cast of Hacksaw Ridge, from left, Hugo Weaving, Gibson, Vince Vaughn, Teresa Palmer, Andrew Garfield and Luke Bracey. Credit:AP The military hardware, however, made it more difficult than shooting Braveheart, his hit 1995 film about the Scottish resistance to English rule – and he says they did it in half the time. Loading Doss resisted having his life story told on screen while he was alive, Gibson says. "They even sent (highly decorated soldier and actor) Audie Murphy from the studios to try to twist his arm," he says. "But he said 'no, I'm just going to pray and grow vegetables'. But he eventually gave his life rights to his church. They said your story might be inspirational to other people and I think he realised that himself later, because his actions encouraged other people after him to go into battle without a weapon, save lives and perform superhuman feats like he did. It's about disregard of self and total humility. What a great story to tell."

Hacksaw Ridge is released in Australia on November 3.