Leonidas (Gerard Butler) uses his shield as shelter from the fierce storm that heralds the arrival of the Persian army to Green shores.

Photo courtesy of Warner Bros. Pictures

Casting Leonidas and Xerxes

Gerard Butler makes a commanding leader as Leonidas, and in fact once played another ancient-world warrior, Attila the Hun, in a 2001 TV movie. But nothing in his diverse resume, including "Dracula," "The Phantom of the Opera" and "Timeline," sold Snyder on the 37-year-old Glasgow native except an in-person meeting.

However, producer Goldmann was mesmerized by Butler’s on-screen presence in 2004’s Dear Frankie. “He’s somebody that you just want to watch, and that’s what makes someone a king—that presence, that ability to hold a room. I think people will look back at 300 and say, ‘That’s the movie that made Gerry Butler a star.’”

Butler, who in real life says he’d “probably be more likened to a puppy dog than any kind of ruler,” jumped at the chance to play Leonidas after reading the script and getting a peek at Snyder’s test clip. “It blew me away. And this was such a cool and kick-ass character to play. The film works on so many levels,” he says. “It's a great story and on the one hand it's informative, but on the other hand it is so cool and visually beautiful while being emotionally powerful and inspirational."

In hindsight, however, “If I thought about what I was about to put myself through, I’d have said, ‘Tell them I’m not interested!’” Butler jokes. He and the otherwise mostly English cast underwent rigorous training to prepare for the movie, but more on that later.

Rodrigo Santoro, a Brazilian actor, was chosen to play the imposing, Persian ruler Xerxes. Historical depictions of Xerxes with a wavy beard and tall hat went out the window in favor of the scary shaven, pierced and chain-covered creature in Miller’s graphic novel, with an otherworldly voice to match.

“Zack told me he wanted the movie theater shaking, so he asked me to speak in as low a register as possible, and he would enhance my voice in the computer to make it echo,” says Santoro. “I tried to portray him as not human. He’s a creature. He’s an entity. So that voice fits, filling the room, together with 7 feet tall and all that.” (He’s actually 6’3”.)

Invited to audition for "300" by Gianni Nunnari, who was familiar with his Brazilian films, Santoro sent in a tape because he was playing Don Quixote in a film at the time, and had lost nearly 40 pounds to do so. “I had to be very fragile and very, very skinny,” he explains, so he had to convince Snyder that he could bulk up to do justice to Xerxes, and did so with workouts and a high protein diet. “I didn’t want to be muscled up, but I had to be this giant figure. Also I had to work with my body to find the right language for this god-king.”

Xerxes (Rodrigo Santoro), the Persian king who claims to be a god, stands atop his elaborate golden litter.

Photo courtesy of Warner Bros. Pictures

Santoro researched Heroditas’ historical accounts to find that Xerxes was a vain, unstable megalomaniac, but also insecure, weak and scared. “I don’t think he’s evil,” says the 31-year-old Rio de Janeiro native, best known in America for films like "Love Actually" and "Charlie’s Angels: Full Throttle," a Chanel commercial with Nicole Kidman and, most recently, playing Paulo on "Lost."

While he agreed to wax and shave off his body hair, a process that gave him new respect for women, he drew the line at shaving his eyebrows, which were instead covered by latex, as were other parts of his face to accommodate several piercings. “I shaved my own head,” adds Santoro, calling it a “freeing experience. I felt like this amphibious creature. It helped me with the character.”

So did getting into makeup and costume, a five-hour process. The chain-laden outfit was “heavy enough to feel the weight of it but I think also it was part of that character—a self-proclaimed god who believed that he really was above everything and everyone on planet earth.”

We'll look at the film's location and its special effects in the next section.