§ Akallabêth The Silmarillion

In this Age, as is elsewhere told, Sauron arose again in Middle-earth, and grew, and turned back to the evil in which he was nurtured by Morgoth, becoming mighty in his service. Already in the days of Tar-Minastir, the eleventh King of Númenor, he had fortified the land of Mordor and had built there the Tower of Barad-dûr, and thereafter he strove ever for the dominion of Middle-earth, to become a king over all kings and as a god unto Men. And Sauron hated the Númenóreans, because of the deeds of their fathers and their ancient alliance with the Elves and allegiance to the Valar; nor did he forget the aid that Tar-Minastir had rendered to Gil-galad of old, in that time when the One Ring was forged and there was war between Sauron and the Elves in Eriador. Now he learned that the kings of Númenor had increased in power and splendour, and he hated them the more; and he feared them, lest they should invade his lands and wrest from him the dominion of the East. But for a long time he did not dare to challenge the Lords of the Sea, and he withdrew from the coasts.