The Old Guard director Gina Prince-Bythewood on Charlize Theron and action movies

It's true, star power matters when it comes to getting big-budget blockbusters to screen. And when you're Charlize Theron, you can get it done.

After kicking literal arse in Mad Max: Fury Road, Aeon Flux and Atomic Blonde, Charlize Theron is a woman who knows her way around an action sequence.

Which is why she was the perfect person to play the lead in Netflix action-drama, The Old Guard, according to its director Gina Prince-Bythewood.

"This character is the best warrior in the world. A woman who's 6000 years old, who knows every single fighting style, and yet there's also an emotional story for her character," Prince-Bythewood told news.com.au.

"Who can embody that? Charlize is a very good actor and she's proven herself there, but she's also proven herself in the action space. And knowing I wanted the action to be grounded and real, I knew she would put in the work and be great in those sequences."

Theron was also crucial in another way, Prince-Bythewood said.

"It was Charlize's involvement in the film that got us the final green light from Netflix."

It's true, star power talks and star power is what many of Netflix's original blockbusters are anchored by. There's no denying scrolling through Netflix's interface stops when you see a face such as Charlize Theron, or Will Smith or Chris Hemsworth.

But what distinguishes The Old Guard from many of those movies is that it balances the demands of an action-packed thriller with the emotional weight of a drama. And you need an actor of Theron's calibre and a director with Prince-Bythewood's commitment to character to pull that off.

Theron's character in The Old Guard – Andromache of Scythia, or Andy – is part of a group of immortal soldiers who lend their formidable combat skills to causes over the years, and by years, it's millennia.

Just as the soldiers are being hunted by an unscrupulous pharmaceutical boss who wants to unlock their DNA for the key to eternal life, they also realise there's another one of them being recruited into their forever ranks.

Given the action-heavy premise of the story, it was crucial to Prince-Bythewood that stunts and combat scenes not be an indistinguishable, fast-edited blur of images, they also needed to tell you something about the characters.

"The best action scenes are those that are character-driven – they have a story, a beginning, an end and emotions," she said.

"There has been shift recently in how they're put together. I remember, and I won't say the name of the movie because I don't want to diss anybody, but there was a very big action movie and I was sitting in the theatre and it was the centrepiece fight, these kids were going after each other, and I just found myself sinking in my seat because I didn't care, there was no jeopardy. People were just punching each other.

"As opposed to Black Panther , which came out about a year later, and I really cared. Every fight had stakes to it, every moment had stakes to it, and that's because I cared so much about the characters.

"I think John Wick was another one that changed the game in terms of not only putting emotion and stakes into the scenes but also being able to see that it was actually the actors doing the work. Because when you do put together a more character-driven action scene, you need the actual actor in there doing it, as opposed to just cutting stunt doubles really quickly, so fast you can't tell.

"I wanted The Old Guard to feel more like an action-drama than a straight action film. With Black Panther and Logan, they have all the elements you love in an action film, but I was sobbing by the end of both of those. Seeing that you could push the genre in that direction really excited me."

In The Old Guard, that included scenes in which these very old characters, who are extremely versed in hand-to-hand combat and older weaponry, would get the better of their modern-day counterparts who have high-powered guns and rifles.

"I wanted it to feel grounded and real," Prince-Bythewood said. "How can we believe that our characters who are fighting with archaic weapons can defeat 16 men who are fighting with modern weaponry?

"Modern soldiers learn to fight from 30, 40 or 50 yards away; they're just shooting an unseen person. Whereas our heroes learnt to fight hand-to-hand, face-to-face with swords. They had to kill up close, and that ability, not having that hesitation, gave them the edge.

"That was something really exciting to bring to an action sequence."

Adapted from comic book writer Greg Rucka's graphic novel of the same name, The Old Guard's screen rights was picked up by Skydance Media, which is also responsible for the Mission Impossible and Jack Ryan franchises.

Prince-Bythewood said Skydance was looking for a female director, adding that Wonder Woman director Patty Jenkins really opened the doors for female filmmakers when it came to action movies.

Best known for her seminal work, Love & Basketball and more recently, Beyond The Lights, Prince-Bythewood had not made an action feature before, but she was champing at the bit.

"Given the way Hollywood acts, very few women get the opportunity," she said. "For a while it felt like a pipe dream but then Wonder Woman happened, and Patty Jenkins rocked it and absolutely opened the door and opened Hollywood's eyes to the fact that, 'Hey, women actually do like the action genre,' and they want to shoot action.

"I loved the story, I loved how it kept surprising me. I loved the characters and what they were struggling with in trying to find a sense of purpose, and who they were, doing good in a world that didn't care about them.

"And then it was two female leads and one of them was a young black woman, which we never get to see. All the elements were there and I dug it so much, and it felt like it was my shot."

The young black female character is played by KiKi Layne, who was phenomenal in her breakout role in Barry Jenkins' adaptation of James Baldwin's If Beale Street Could Talk. Even though Layne had never done action before, Prince-Bythewood was confident the young actor would pick it up.

"I knew within five seconds of her audition that she had that innate toughness that (Layne's character) Nile needed," the director said. "Her passion for the character, her passion to be great in this space, convinced me that she would put in the work, and she never wavered.

"Charlize trained with KiKi and Kiki got to see how hard you have to work to get there. Charlize was a good example of that. Both of them came to this thing wanting to be great."

In a career spanning almost three decades, Prince-Bythewood has been an advocate of telling stories about black Americans, something that has never been easy. But it's starting to change, and Layne's co-lead role with Theron is just one gear in the machine.

"Putting black women on screen in leading roles is absolutely the hardest thing to do in Hollywood. I feel like I've been in a sustained fight for 20 years to do that," she said.

"Finally, I have my next two projects lined up – they both star black women and they're both really big projects. And for the first time in my career, it wasn't a fight. I'm hoping that momentum continues."