Did Sauron ever betray Morgoth?

Question

Sauron was given the title "Sauron the Deceiver" because he used charm and deception to gain control over others. He taught ring-craft to the elves and gave Rings of Power to men and dwarves so that he could use the One Ring to bind others to his command.

Sauron was also called "The Deceiver" because he convinced Ar-Pharazôn, a Númenórean king of the Second Age to institute Melkor (Morgoth) worship. His deceptions led to the downfall of Númenór.

Here are a few quotes that describe his ability and willingness to deceive.

Sauron took to himself the name of Annatar, the Lord of Gifts, and they [the elves] had at first much profit from his friendship.

^{_{Of the Rings of Power and the Third Age}}

In Eregion Sauron posed as an emissary of the Valar, sent by them to Middle-earth ("thus anticipating the Istari") or ordered by them to remain there to give aid to the Elves. He perceived at once that Galadriel would be his chief adversary and obstacle, and he endeavoured therefore to placate her, bearing her scorn with outward patience and courtesy.

^{_{The Silmarillion V : Of the Rings of Power and the Third Age}}

He could assume many forms, and for long if he willed he could still appear noble and beautiful, so as to deceive all but the most wary.

^{_{The Silmarillion V : Of the Rings of Power and the Third Age}}

Understanding he turned to subtlety in perverting to his own will all that he would use, until he became a liar without shame.

^{_{*The Silmarillion II : Valaquenta "Of the Enemies"}}

When Thangorodrim was broken and Morgoth overthrown, Sauron put on his fair hue again and did obeisance to Eönwë the herald of Manwë, and abjured all his evil deeds. And some hold that this was not at first falsely done, but that Sauron in truth repented, if only out of fear.

^{_{The Silmarillion V : Of the Rings of Power and the Third Age}}

We know that Sauron wished to become a dark lord in his own right.

Though of immensely smaller native power than his Master, [Sauron] remained less corrupt, cooler and more capable of calculation. At least in the Elder Days, and before he was bereft of his lord and fell into the folly of imitating him, and endeavouring to become himself supreme Lord of Middle-earth. While Morgoth still stood, Sauron did not seek his own supremacy, but worked and schemed for another, desiring the triumph of Melkor, whom in the beginning he had adored.

^{History of Middle-earth X Morgoth's Ring Part 5: "Myths Transformed" Orcs}

The above quote says that Sauron both wanted to become supreme Lord of Middle-earth, yet also worked for the supremacy of Morgoth. Seems like his adoration of Morgoth could have been false just as friendship with the elves was false.

Given that he misled elves and men and dwarves, did he also mislead or betray his own master?

Answer 1

The only thing we know about Sauron during the First Age is that he captured Tol Sirion and held it until he was eventually defeated by Luthien and Huan. After that, he disappeared and kept in hiding. Possibly because he feared Morgoth's wrath, since Sauron's defeat had made it possible for Luthien to create the disguises used when she and Beren infiltrated Angband and stole a Silmaril. It's far-fetched to call this betrayal though - he was simply defeated.

So as far as we know, Sauron didn't betray Morgoth at any point, since he had neither a motive nor something to gain from doing that.

Answer 2

At least in the Elder Days, and before he was bereft of his lord and fell into the folly of imitating him, and endeavouring to become himself supreme Lord of Middle-earth. While Morgoth still stood, Sauron did not seek his own supremacy, but worked and schemed for another, desiring the triumph of Melkor, whom in the beginning he had adored.
_{History of Middle-earth X Morgoth's Ring Part 5: "Myths Transformed" Orcs}

To me, the sentence reads as "before he ... fell into the folly of imitating ... and endeavouring." So the way I understand it, Sauron didn't start endeavouring to become himself supreme Lord of Middle-earth unfil after he was bereft of his lord.

Answer 3

Yes, kind of.

We have no information on him actually plotting on his masters overthrow, but at least on one occasion he clearly placed his interest in front of Melkors, and acted to his masters wrong. It is the incident Amarth mentions:

But no wizardry nor spell, neither fang nor venom, nor devil's art nor beast-strength , could overthrow Huan without forsaking his body utterly. Ere his foul spirit left its dark house, Luthien came to him, ghost be sent quaking back to Morgoth; and she said: 'There everlastingly thy naked self shall endure the torment of his scorn, pierced by his eyes, unless thou yield to me the mastery of thy tower.'

Then Sauron yielded himself, and Luthien took the mastery of the isle and all that was there; and Huan released him. And immediately he took the form of a vampire, great as a dark cloud across the moon, and he fled, dripping blood from his throat upon the trees, and came to Tar-nu-Fuin, and dwelt there, filling it with horror.

Then Luthien stood upon the bridge, and declare her power: and the spell was loosed that bound stone to stone, and the gates were thrown down, and the walls opened, and the pits laid bare; and many thralls and captives came forth in wonder and dismay, shielding their eyes against the pale moon light, for they had lain long in the darkness of Sauron.

Silmarillion, Of Beren and Luthien

So when he was threatened with death (and being sent back to Morgoth unhoused), he gave over the stronghold he held as Lieutenant of Melkor, allowing the enemy to demolish the strategic fortress and free the prisoners. So he did not commit actual High Treason, but could have been held treasonous and executed under many real word regimes for this.

After this Luthien proceeded in disguise to Angbad, also overwhelming Melkor. We have no direct information on this, but considering how careless his master was with Luthien, it is quite possible that Sauron did not tell the full thruth when he reported the events to Melkor.