[Macalaure]

I think it's interesting that Morgoth did wage war against Doriath, as we see from the many battles over Dimbar, but still never dared to attack the Girdle.

We know that the Girdle could only be breached by someone of greater power than Melian. This rules dragons out and leaves Sauron and the Balrogs.

Beyond lay the wilderness of Dungortheb, where the sorcery of Sauron and the power of Melian came together, and horror and madness walked.
~ Of Beren and Lúthien

This gives me the impression that Melian's power and Sauron's sorcery is approximately equally strong. So, even though we would consider Sauron to be more powerful overall, it is doubtful to me whether he would have been able to break through the Girdle with his sorcery. It's not overall power which counts, but specific powers. Maybe Sauron would have been able to, maybe not, but I don't think it would be certain. We also know how patient Morgoth is and how calculating with his resources (except Orcs). He wouldn't have risked his most mighty servant in an attack of questionable success. Gothmog and the balrogs are lesser Maiar than Sauron (esp. in sorcery), so an attack of them would be at least as much of a risk.

In the end, Morgoth would probably have had to break the Girdle by himself, but he was extremely reluctant to even leave Angband. I don't think he would have dared to, unless Doriath was the only realm left in all Beleriand. Morgoth basically restricted the power of Doriath to Doriath itself, to the effect that he didn't have to fear it anymore. This way he was able to delay the problem to whenever he felt the time had come to deal with it.


A minor tangent:

Originally Posted by Rune

I only remember two ever passing the gridle and that was Beren which Melian predicted would do so and then Carcharoth, but I don't think that Carcharot would have been able to do so with out the Silmaril.

You're right, but it was not the power of the Silmaril that enabled him.

Nothing hindered him, and the might of Melian upon the borders of the land stayed him not; for fate drove him, and the power of the Silmaril that he bore to his torment.
~Of Beren and Lúthien

It was not the Silmaril that increased Carcharoths power, even though it made him much more frightful than before, but because he carried the Silmaril it became his fate to enter Doriath.