Code Geass: Lelouch of the Rebellion

A year has passed since "The Black Rebellion" and the remaining Black Knights have vanished into the shadows, their leader and figurehead, Zero, executed by the Britannian Empire. Area 11 is once more squirming under the Emperor's oppressive heel as the Britannian armies concentrate their attacks on the European front. But for the Britannians living in Area 11, life is back to normal. On one such normal day, a Britannian student, skipping his classes in the Ashford Academy, sneaks out to gamble on his chess play. But unknown to this young man, several forces are eying him from the shadows, for soon, he will experience a shocking encounter with his own obscured past, and the masked rebel mastermind Zero will return.

The Empire of Brittania has invaded Japan using giant robot weapons called Knightmare Frames. Japan is now referred to as Area 11, and its people the 11s. A Brittanian who was living in Japan at the time, Lelouch, vowed to his Japanese friend Suzaku that he'd destroy Brittania. Years later, Lelouch is in high school, but regularly skips out of school to go play chess and gamble on himself.
One day, he stumbles on terrorists 11s who've stolen a military secret and is caught by a member of the Brittanian task force sent after them, who is Suzaku. As the rest of the squad arrives, Suzaku is shot for disobeying orders, while the military secret, a young girl, gives Lelouch the power to make anyone obey any order. He takes command of the terrorists and leads them to crush the approaching Brittanian force. However, Suzaku is secretly made the pilot of Brittania's brand new test model Knightmare, Lancelot. Lelouch becomes the masked king Zero to lead the rebellion to defeat Brittania.