Director Jean-Luc Godard once said all you need to make a movie is a girl and a gun. The new adventure film “Heart of the Beast” shows that all you need to make a movie is Brad Pitt and a dog. Aside from a few brief moments with other characters, the film focuses entirely on Pitt’s special forces veteran James and his beloved canine companion, Odin, as they struggle to survive in the Alaskan wilderness after a plane crash. It’s a simple, straightforward premise — but making it work cinematically and emotionally was no easy task.

“It was a bigger challenge than I understood going into it,” director David Ayer told IndieWire on the Filmmaker Toolkit podcast. “I really didn’t know what I was in for.” Although Ayer had staged massive battle sequences in his previous collaboration with Pitt, the World War II drama “Fury,” he found that stripping the action down to one actor and a dog created its own set of difficulties. “The simplicity of it exposes the filmmaking in ways I never imagined. Your decisions, tone, mood, and performance count more than ever in that situation. There was nowhere to hide.”

Ayer came on board the film after reading Cameron Alexander’s script, which provoked such a strong emotional response that the director couldn’t resist taking the material on. “I think  it triggered part of my own grief over the loss of my father when I was young, and this sort of aspirational desire in me,” Ayer said. “I wish I had someone who looked after me the way James looked after Odin. I wish I had that kind of unconditional love and support.”

Exploring that kind of emotional connection through a tough, male-oriented action movie fits Ayer’s sensibility, as he’s made a career out of poking and prodding assumptions about masculinity. From his brilliant screenplay for Ron Shelton’s cop drama “Dark Blue” to directorial efforts like “Harsh Times” and “End of Watch,” Ayer has frequently explored and challenged conventional cinematic notions of violence and heroism, something steeped in his own military background.

In “Heart of the Beast,” Pitt is the ideal partner for Ayer’s preoccupations. The actor gives one of his best performances in a film that hinges almost entirely on his ability to express emotion and thought with minimal dialogue. In his collaborations with Ayer, he tends to be both tougher than in other movies and more vulnerable; Ayer uses the star’s persona and finds new textures and meanings in it, the same way John Ford once did with John Wayne, or Don Siegel did in his films with Clint Eastwood.

“ I think it has to do with his willingness to jump into material that isn’t so traditionally engineered as a movie star role, or traditionally masculine,” Ayer said. “He’s open to the deconstruction. And he has a lot of range, and I feel like he doesn’t always have the opportunity to find those dichotomies in himself. Maybe there’s also a kinship there in our understanding of traditional masculinity, the masks men are given in life to wear, and the fact that there’s often a confused beating heart beneath them.”

Digging into the character was all the more challenging for both Pitt and Ayer given the compressed pre-production schedule and swift shoot, which required them to hit the ground running. “It was a whirlwind, so it really put Brad on the spot as an actor, and me on the spot as a director,” Ayer said. The key to pulling it off was close collaboration with his department heads and lead actor to make sure James’ arc was clearly mapped out, both visually and emotionally.

“I had an amazing production designer, Greg Berry, and we came up with this visual journey that reflected the inner journey of the character,” Ayer said. “Brad’s very internal, so much of our work came in prep, mapping out the emotional beats and the tone. And then once he gets to set he will grind and exhaust himself.” According to Ayer, that exhaustion showed up in the movie, as Pitt couldn’t relax or rely on the typical comforts of a film set.

“Normally on a set, you have the director’s chairs lined up, and the actors sit in them and socialize,” Ayer said. “He had nowhere to go other than to be cold and tired and emotionally exhausted by himself. They say acting is reacting, and he didn’t have a big cast to react to and pass that energy back and forth — he had to react to the circumstances. He’s not getting any of the normal support an actor would in a scene. It was like a jet pilot flying a solo mission.”

Ultimately, Ayer credits Pitt, his crew, and serendipity for everything coming together so smoothly. “All of the details come from a lifetime of experience,” Ayer said. “ Brad’s done an amazing amount of movies and was in a place where he was willing to be vulnerable in ways he hasn’t before. I’ve done a few movies and feel like I’m just beginning to come into my own, and I was open to really challenge myself both emotionally and as a filmmaker. So everything came together.”

To hear the entire conversation with David Ayer and make sure you don’t miss a single episode of Filmmaker Toolkit, subscribe to the podcast on Apple, Spotify, or your favorite podcast platform.