As the director of one of the most successful film franchises of all time, Christopher Nolan sits on the Hollywood throne of the action movie genre. The Batman trilogy from DC was lauded by the Academy and heralded at the box offices to the tune of $2 billion.

How did Nolan reboot a fictional superhero into a global phenomenon? According to him, the key was to expand Batman's story and tell it from a novel perspective.

"My pitch was, at the time, ‘let’s treat this with some sense of reality.’” Nolan said in a 2008 interiew. “Not so much a comic book movie as an action film. Really, the idea of an extraordinary character in an ordinary world.”

In order to revamp the classic Batman comic and bring a sense of authenticity to the movies, however, Nolan had to remember the big picture and the nitty-gritty, starting with who would be cast as Bruce Wayne.

Related: There Will Be More Than One Batman In DC's Upcoming 'Flash' Movie

In ‘Batman Begins,’ Christian Bale Brought Nolan's Vision to Life

In a bonus interview from Batman Begins, Nolan explained why Christian Bale was the right actor to don the Batman suit.

“Christian was the first actor I met with actually. And it was clear to me, looking into his eyes, that this was somebody who can make you believe in the possibility of someone devoting their life to something this extreme.”

Nolan went on to explain how Bale’s focus and research on the original Batman helped him shape his character.

“Christian had a very controlled and specific approach to how he wanted to portray the aggression of this character, the animal-like quality. He talked a lot about having Batman crouching in the shadows, and he’s constantly sort of crouched on the railings or the sides of buildings, very much the way he is in the comics.”

Related: What Christian Bale Thinks Actually Happened At The End Of 'The Dark Knight Rises'

Christian Bale’s Physicality Mattered to Christopher Nolan

When Bale learned that he was first in line to play Bruce Wayne, he had an enormous amount of training to do as he had just finished filming The Machinist, a movie that required him to lose 60 pounds.

“I was just stuffing my face all day long and lifting heavy weights,” Bale said in the interview. However, he ended up gaining too much weight and reached about 220 pounds.

“I took Chris [Nolan] at his exact word about ‘get as big as you can’ but he didn’t really think I was going to get that big,” Bale said, laughing. “A number of the crew I’d worked with on previous movies, they looked at me and they were like, ‘Chris, what are we doin’ here, fat man or Batman?’ I realized, okay, that’s not what he had meant. So, I had to try and lose a lot of weight.”

With the help of an on-set trainer, Bale lost some of the weight and built up his stamina and muscle tone to create Christopher Nolan’s ideal Batman look.

The Evolution from ‘Batman Begins’ to ‘The Dark Knight’

After the tremendous success of Batman Begins, Nolan faced another challenge: he had to keep the story of Batman going and make it even more incredible.

“We were trying to figure out, ‘how do you move on from what you’ve done in Batman Begins? How do you make the film bigger and more than Batman Begins, without compromising the story and the characters and everything?’” Nolan asked in an interview following The Dark Knight release. “And I wanted to push further and further in the direction of shooting on location and shooting with a real-world scale … shooting on real locations, you’re able to get some of that scope and some of that scale very naturally and organically into the film.”

Nolan also chose to expand Batman’s story in The Dark Knight and explore the harsh realities of the universe.

“It was always going to be tricky to change the focus of the movie from [Batman Begins] being just about Batman to being about so many other characters,” he said in a 2010 interview with Movie Web. “But that was very much a requirement of what the story was going to be. We wanted to tell this sort of epic crime story, this city story based on … law enforcement, the justice system … and the mobsters and the gangsters, the way they interact with the Joker. But I think there’s an overriding sense that … who Batman is and how people respond to him is actually the defining feature of the story.”

Related: What The Cast Of 'The Dark Knight' Has Said About Working With Heath Ledger

Nolan’s Vision for ‘The Dark Knight Rises’

When The Dark Knight Rises was released, fans and critics were astonished that Christopher Nolan was once again able to match his previous work. In an interview with Movieclips Coming Soon, however, Nolan revealed that he was not thinking of how to surpass his audience’s expectations when he began working on The Dark Knight Rises. Instead, he was thinking of the third film as a continuation of the story.

“To be honest, we only go into a film if we know that we’ve got a story to tell, and we really felt like we needed to finish this story,” Nolan said.

Nolan also explained how the cast was able to make the continuation of the Batman story so enthralling. In particular, he had high praise for Anne Hathaway, who played Cat Woman.

“She could portray the interior life of the character with great authenticity and relatability, but she could also be very expressive and inhabit a larger-than-life character," he explained.

With the ideal cast, careful planning, meticulous writing, and a clear vision, Nolan was able to revamp the classic Batman comic and create a billion-dollar cinematic success. The trilogy will still be considered one of the best action-movie franchises for years to come.

Next: All Of The Dark Knight Trilogy Villains, Ranked