The Revenant is the brainchild of Mexican director Alejandro Gonzalez Inarritu, and it took him five years to make. The 52-year-old filmmaker won the Academy Award for Best Director for Birdman at last year's Oscars and is one of the most revered filmmakers in Hollywood after the critical success with dramas 21 Grams (2003), Babel (2006) and Biutiful (2010).  A 'revenant' describes someone who has returned from the dead, which aptly describes the storyline here.

The Revenant tells the story of Hugh Glass (played by Leonard DiCaprio), a legendary figure in 19th-century American history and is inspired by actual events. Glass was mauled by a grizzly bear while guiding a group of fur trappers from the Rocky Mountain Fur Company in unchartered territory on an expedition up the Missouri River on the American frontier in the autumn of 1823. The guide was severely injured in the attack, suffering deep lacerations to his back, shoulder and neck. One leg could not hold his weight.

The bear attack is a terrifying piece of cinema, and gives you a gripping take on what it really might be like to fight one. A real grizzly was filmed and then cleverly welded with footage of DiCaprio – there is minimal CGI. Audiences "will practically feel the breath of the bear," DiCaprio says.

"This scene is one of the most incredible cinematic experiences I think audiences will ever have. It was a difficult and arduous sequence to put together, but it ended up profoundly moving because of Alejandro's ability to put the audience in the middle of the scene."

Inarritu is blunter when describing the scene.

"Nobody would ever have experienced a scene like that – you'll shit your pants."

The film begins with the expedition losing 34 men in an ambush by Arikara​ Indians. Fearing they would all perish at the hands of the warring braves, Captain Andrew Henry (Domhnall Gleeson) employs two men – John Fitzgerald (Tom Hardy) and the younger Jim Bridger (Will Poulter) – to stay behind with Glass's half-Indian son Hawk and wait until the guide dies before burying him properly.

However, Glass clings to life. Growing impatient, and fearing for his own life, Fitzgerald murders Hawk in front of his father's eyes in the absence of Bridger. He then drags Glass's crippled body to a shallow grave and quickly covers him with dirt before taking his gun and knife. Fearing an attack by Indians, both Bridger and Fitzgerald leave him to die there.

The betrayal by his minders and murder of his son fuels Glass to crawl out of this grave and embark on a gruelling journey to exact his revenge on them.

"It is a very simple story of a man trying to find a reason to live," Inarritu explained, on a visit to a Hollywood editing suite during the film's production. "There was something attractive to me to make an adventure film, a sort of violent adventure film, and the reasons you survive. If at the end you have lost basically everything, what gives human beings that instinct to keep breathing, to grasp the last breathe. Why is that?"

Inarritu took his first trip to scout untouched, natural locations five years ago – it was an exhaustive process.

"It really took me a lot of time to go there and find these locations that I not only wanted to be really virgin, and not man-touched and that you can really feel what those men really felt," he said.

"Because the problem with now, the location in nature, is that now they are manicured by humans, they are parks or things, and you feel already that it has been touched."

Inarritu, along with co-script writer Mark Smith, took Michael Punke's fictional account in a book of the same name and made some key changes to the story. The most important one was to create an indigenous wife and son for Glass, who, according to some accounts, lived with the Pawnee​ Indians for a period before this fateful expedition. It gives the survivor motivation to live for revenge, examines the pain of grief and adds a layer of love to this bloody and violent film.

The Revenant is much more than a story of revenge, however, and the film's leading man knew it would be much more than a Hollywood action flick in the hands of Inarritu. Leonardo DiCaprio is brilliant as Glass – his performance is already generating a buzz for his first Academy Award having been nominated for a Golden Globe.

"He's a great visionary, and there are very few filmmakers like him who can make a poetic, existential epic piece," DiCaprio says. "Here, you have a linear story which is somewhat of a campfire legend of American history: the American survivalist, the fur trapper, the mountain man mauled by a bear, then travelling hundreds of miles through the harshest conditions, driven by instinct.

"But through Alejandro's eyes it became something much more than that.  It tells a story of triumph of the human spirit and what it is to overcome massive obstacles. It became less of a revenge story and something, I think, much more profound than that."

After enrolling in a boot camp to learn basic wilderness survivalist skills of the time, such as starting a fire with flint, cutting pelt and hunting with a muzzle-loading rifle, the cast had to traverse icy, wild rivers, hike through snow-covered alpine trails with soaking clothes and throw themselves into fierce combat scenes in the bitter, freezing cold and mud. It is a far cry from the glamour of Hollywood or the comforts of modern life for that matter. And it is just what the director wanted. The harshness of the locations helped make the performances more authentic and bring an incredible tale of survival to life in the wilderness setting.

The production was just as epic as the tale – it was a long shoot for a variety of reasons. The film was shot in chronological order, starting in autumn. And, because Inarritu used only natural light, the cast and crew sometimes only had 40 minutes a day to film in remote locations. Poor weather hampered the crew – a flood at one point closed down production, dangerously cold conditions stopped shooting and then finally a lack of snow meant the final scene had to be completed in Argentina.

"Yes, we had a lot of problems, [it was] really difficult," Inarritu says. "We were shooting one day at 30-something below zero [Fahrenheit or -34 degrees Celsius] with the wind chill – it was much more than that."

And to keep it closer to reality, Inarritu also used as little computer generated imagery as possible – most of it to do scenes where animals are shown to be hurt.

"Unfortunately there are many films relying on [CGI] so much on that that everything looks like a video game," he says. "I have very few, few [visual effects]. The ones are there are the ones that are extremely necessary – or it would not be impossible."

Inarritu sounds every bit the visionary artist when he describes his ambitions for the film.

"I think the natural light, and not relying on visual effects, that's what really makes it challenging and beautiful," Inarritu says. "I want this to be like a sonic painting, you know. I want this to be a painting that you can get lost in. You live the 19-century like really that nobody has really [shown]."

The director also uses long shots – a technique he employed to surreal effect in Birdman. In The Revenant it heightens the sense of drama and takes in the sweeping scenery and isolation at the same time. The effect is compelling – especially in the action sequences. The ambush scene where Indians descend on the trappers is stunning and violent and clearly complex as multiple skirmishes happen simultaneously.

Given the limitation of shooting time and the complexity of the long shots, the cast had to rehearse highly choreographed scenes and stay focused – the preparation and the film shoot itself were intense, according to DiCaprio.

"We submerged ourselves in these elements and had to plan accordingly for what was going to happen," he says. "To bring the film to life, we worked for months to prepare for and execute well-choreographed shots, we learned everything we could about the time period – reading as much as we could – but at the end of the day, nature consumed all of it.

"We tried our best to make this film like a documentary, and almost like virtual reality in a lot of ways."

DiCaprio says Inarritu's painstaking attention to detail, long takes and lighting techniques provide a stunning end result.

"You see a vast landscape and massive bloody battles, but at the same time the camera snakes in on a small close-up of somebody to capture a moment, and then moves along," he says. "I don't think there's ever been a film like it.

"It's one of those highly-ambitious movies that we don't see from the Hollywood studio system very often."