[Beanamir of Gondor]

I'd like to avoid the whole Nauglamir argument that's going on, because I'm the chess amateur William Cloud Hickli mentioned before, and skip back to what the Dark Elf contributed to the conversation a while back.

Originally Posted by Morthoron

I think Carcharoth's fate was wound inextricably with the Silmaril, yet so was Huan the hound's doom. Carcharoth was bred by Morgoth to be Huan's bane; therefore, the passage referring to Carcaroth's fate has the further inference of meeting Huan at last in mortal combat. Breaking the Girdle of Melian was due to the Silmaril, and Carcharoth's fate was to meet Huan in Doriath.

One also has to wonder about Melian's awareness of these things. If it were fate for Carcharoth to pass the Girdle, would she have precognition of it: i.e. was it impossible for her to stop it, because she knew it would happen no matter what? She predicted that Beren would arrive in Doriath, so he was not hindered when he arrived, alone and unintentionally trespassing. Much the same, she might have known that Carcharoth was heading into Doriath, but (look out! a digression!) like Beren, he was unwitting in his trespass, and didn't need to be hindered, and wasn't directly attacking the kingdom.
That ties into something Rikae said earlier:

Originally Posted by Rikae

However, does this mean that Morgoth, having the Silmarils, could just stroll into Doriath any time he wanted? There is more to it that a simplistic "get a Silmaril, be more powerful than anybody" dynamic at play, I think. Maybe even a sense of the Silmarils themselves having, in a way, a will of their own, as the one ring does? Or not so much a will, but a destiny?

Morgoth had three Silmarils in his possession for quite a long time, and he didn't just wander into Doriath and attack Menegroth. I think that has quite a lot to do with Beren and Carcharoth (not to draw too many parallels between the two) unwittingly wandering into Doriath, without knowing specifically that they had crossed the Girdle of Melian. They were alone and, for the most part, unarmed. Now if Morgoth, on the other hand, had gathered all his forces and directly attacked Doriath, Melian's Girdle would have been strengthened for war, and she could have held back at least some of Morgoth's forces. It wasn't just one lone Man or Wolf wandering in through the mists.
It's a lot easier for one soldier to slip across the lines than it is for an army to march in. regardless of which war we're talking about.