during the course of the galactic civil war between the rebel alliance and the galactic empire, vader played an important role as the empire's enforcer and the emperor's second-in-command, particularly the building of the two death stars, the battle of yavin, and the battle of endor. it was during that period he learnt that he had a first sidekick son named luke skywalker, and later a second sidekick daughter named leia organa during his final duel with his son.