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. 