[lathspell]

In the Beginning of the First Age Sauron was a Maia in the service of Aulë. He was corrupted by Melkor in a very early stage and became his chief servant (later he was called 'the Lieutenant of Angband'). After the wars and the downfall of Thangorodrim, Melkor or Morgoth was cast into the void. Sauron almost turned aside from evil, but after a while he went to Barad-Dur and he wanted to conquer the lands there. He was doing very well, but than the Men of Numenor came sailing to Middle-earth. After a very long time the Numenoreans began to make a war upon Sauron and they took him to Numenor as a prisoner. There he was as a prisoner... at first. But Sauron was cunning and talked his way from prisoner to primary counsellor of the King of Numenor. In that position he sickened the hearts of the Numenoreans. They were corrupted and deceived, for Sauron told them that the Valar were scared of them and that could conquer Aman and be immortal and that the 'Lord of All' was Melkor. Many believed him and went to conquer Aman, but some were faithful and they were called the Elendili. The Valar did nothing but call for the aid of Eru and he created a great whirlpool and in it all the ships of the Numenoreans were destroyed and the whole island sunk to the bottom of the ocean. Sauron himself could hardly escape, but he lost his form that day. The Elendili were swept far over the Sea to the shores of Middle-earth. Elendil was their leader and their they made the realm of Gondor for the thread of Sauron was long away. But Sauron returned in a fair disguise and he had given himself the name of Anatar which means (I don't have the books and do not know if I'm wholly right here): Lord of Gifts. He was befriended with the Elves in that time for he learned them many things and they were eager to learn it. So he learned them to make the Rings of Power and he ensnared them, or tried to ensnare them, in that way. The Elves were aware of him when he had the One Ring around his finger and hid the three, and at last they formed the Last Alliance and Sauron was thrown down ones more and the Ring could have been destroyed then, but Isildur kept it, and he was betrayed. Afterwards the Ring came through long ways in the hands of Bilbo. And Sauron was at that growing again in Dol Guldur.

The rest of the tale is known to all here, I guess.

Now for the answer:
In all things Sauron did he was always nurtured by Morgoth. Morgoth still could return as prophecies told, but only when the High King (Manwe) was thrown down from his throne on Taniquetil on Aman. Sauron was always the servant of Morgoth, but he was the thread in later days, not Morgoth. So Sauron was then the Dark Lord, for he was the main problem.

Hoping this rather long answer will help

Greetings,
lathspell