Mothma and Senator Bail Organa of Alderaan watched in dismay as Supreme Chancellor Palpatine used the Clone Wars as an excuse to claim more power. Concluding Palpatine had become an enemy of democracy, they formed a secret organization to oppose his rule.
The resistance organization founded by Mothma, Bail Organa and like-minded Senators became the Rebel Alliance. Mothma served as its civilian leader, emphasizing that the Alliance's goals were to restore the Republic.
After Palpatine became Emperor, Mothma went into hiding, aware that her outspoken opposition had earned her a death sentence. Imperial agents hunted her, eager to eliminate one of the Rebellion's most visible leaders.