Executives at Warner Bros. had no idea what they were dealing with when they began to slap together a big-screen adaptation of Alan Moore’s seminal 1980s graphic novel, Watchmen. Luckily, the suits happened to hire a devotee in 300 director Zack Snyder. “They called and said nonchalantly, ‘Would you like to direct this superhero movie Watchmen?’” recalls Snyder. “They didn’t give a rat’s ass. But as a fan, I had to try to do Watchmen justice.”

Considering Moore’s 400-plus-page tome is one of the most influential, genre-busting graphic novels of all time, keeping the source material intact was top priority for Snyder. Set amid the Cold War paranoia of 1985, Watchmen follows—with backstories upon side plots—a retired superhero team that is mysteriously being killed off. Initially, the studio planned a reimagining that updated Watchmen’s universe into more relatable Iraq war times. “I shook the execs’ hands,” says Snyder, “then went off and wrote the script exactly as it was in the comic. They weren’t happy.”

Snyder’s $71 million opening weekend for 300, however, gave the studio the confidence to flash a green light. Two years later he just may have pulled off something other A-list directors could not over the project’s 20-year development: translating Watchmen into a feature-length spectacle. Such an ambitioussuper­­hero film was once too risky, but thanks to The Dark Knight, taking caped crusaders seri­usly—with such human foibles as obsessionand impotence—is no longer taboo. “This isn’t for kids,” warns Snyder of scenes that earned Watchmen’s R rating. “The Dark Knight is dark, sure, but not being able to get an erection around a sexy girl because you don’t have your hero suit on? That is dark.”