There wasn't a war that he had to attend to. No body knew about him because he works in the shadows with no companions. He does not need people to help him fight to kill one person, he killed Darth Vader, he killed countless Jedi Sith all by himself, he took a star destroyer out of the air with only the force, he destroyed army's of both Imperials, and wookies all by himself, and he did all of these with ease while being an apprentice.