[Bella:] This was the ploy. [Caius] had not wanted Irina's complaint; he had wanted her defiance. His excuse to destroy her, to ignite the violence that filled the air like a thick, combustible mist. He had thrown a match. (37.66)
Bella realizes that Caius tried to start the war in a way that would pin the Cullens and their friends as the aggressors, and the Volturi as victims, forced to act in self-defense.