[Mithadan]

In answering Urwen's question, one must keep in mind the nature of the War of the Jewels. It was fundamentally unwinnable. The Noldor, even allied with Men and the Dwarves of the Ered Luin, could never defeat Morgoth. They might hinder his plans, stymie his movements and slow his advances. They might even win a battle or two, but they could never win the War. The destruction of the Noldorin realms in Beleriand was inevitable. Doriath was not a Noldorin realm, and I will address it last.

Nargothrond - Ulmo warned Finrod and Turgon "to prepare for a day of evil, and to establish a retreat, lest Morgoth should burst from Angband and overthrow the armies of the North." He did not suggest that either could withstand Morgoth. The Fall of Nargothrond was the result of a succession of errors, with Turin, his bridge and the open defense of the realm being just the latest in a series of contributing events. And he was under Morgoth's curse. There is a detailed thread on Morgoth's curse upon Hurin and his house in the Books Forum with the most recent posts being within the past year. Finrod may have erred in admitting Curufin, Celegorm and their people into Nargothrond after Dagor Bragollach. Curufin and Celegorm poisoned the realm and suborned his rule. Their speeches after the arrival of Beren caused Nargothrond to cower in fear and avoid open conflict. Orodreth allowed this policy to continue. All these things contributed to the fall of Nargothrond, but it was inevitable. Turin bore some responsibility for the fall of Nargothrond but certainly no more than others.

Gondolin - Maeglin's treason may have revealed the location of Gondolin and the routes to enter Tumhalad. He may have been a contributory cause without which Gondolin might have survived for some time longer. But, it was Turgon who rejected the counsel of Ulmo conveyed to him by Tuor, "Love not too well the work of thy hands... the true hope of the Noldor lieth in the West, and cometh from the Sea." If Turgon had heeded the words of Ulmo, his kingdom, though not his city, may have survived.

Doriath is more complicated. It was not a Noldorin Kingdom. It did not fall under Mandos' prophecy (or curse as some have said), at least until... Thingol decided to be clever and sent Beren off to secure a Silmaril, tying Doriath into the ill-fate of the Noldor. And, Thingol could have swallowed his pride and returned the Silmaril to the Feanoreans. Hurin only brought the Nauglamir which led Thingol to summon Dwarven smiths. But the Nauglamir was an excuse for the Dwarves. They were seduced by the Silmaril.