X2 (also marketed as X2: X-Men United, and internationally as X-Men 2) is a 2003 American superhero film directed by Bryan Singer and written by Michael Dougherty, Dan Harris and David Hayter, from a story by Singer, Hayter and Zak Penn. The film is based on the X-Men superhero team appearing in Marvel Comics. It is the sequel to X-Men (2000), as well as the second installment in the X-Men film series, and features an ensemble cast including Patrick Stewart, Hugh Jackman, Ian McKellen, Halle Berry, Famke Janssen, James Marsden, Rebecca Romijn-Stamos, Brian Cox, Alan Cumming, Bruce Davison, Shawn Ashmore, Aaron Stanford, Kelly Hu, and Anna Paquin. Its plot, inspired by the graphic novel God Loves, Man Kills, concerns the genocidal Colonel William Stryker leading an assault on Professor Xavier's school to build his own version of Xavier's mutant-tracking computer, Cerebro, in order to destroy every mutant on Earth and to save the human race from them, forcing the X-Men to team up with the Brotherhood of Mutants, their former enemies, to stop Stryker and save the mutant race.