[Formendacil]

In tandem, I think, with Morm's thoughts, Gandalf' return was necessary as a sign of the importance of the battle against Sauron. Without Gandalf, the battle is something of a "small nations vs. Mighty Aggressor" sort of battle. Honourable, to be sure, and definitely worthy and in need of fighting.

With Gandalf the White there, however, the battle takes on a more... how shall I say it?.. spiritual dimension. It ceases to be merely "good guys vs. bad guys" and becomes Good vs. Evil. Without Gandalf, we lose the potent symbolism of White against Black. Also, Gandalf's power acts to help us see the sheer power of Sauron. Without Gandalf, Sauron's defeat at the hands of a Hobbit merely goes to show that he is fallible and defeatable, that he was defeated by a "mere" Hobbit.

Gandalf's presence, however, since we are shown his great power and authority, highlights Sauron's own power, since Gandalf finds himself with his hands full against the Witchking. This, in turn, makes the defeat of Sauron that much more eucatastrophic, since we are more clearly aware of just how powerful Sauron (and the Ring) is.

Continuing with the idea of spiritual importance, Gandalf is a clear symbol of there being a "Greater Power" involved- whether you're considering this greater power to be just the Valar, or Eru Himself. This is in agreement with Tolkien's strong Catholic feelings. The fight of Good is aided by above. We are not just fighting on our own, or for ourselves, but on behalf of Good everywhere. Without Gandalf the White, the Lord of the Rings loses the integral sense that it has of Right vs. Wrong.

And I agree with Anguirel that this makes it different from the Silmarillion. But it is a NECESSARY and INTENDED difference. The War of the Jewels, though a war of good vs. evil is NOT a war of Right vs. Wrong. The Eldar, though they remain the good guys, are essentially waging an unsanctioned war- a war that should have had the support of the Valar to be truly Right. That is why they continued to suffer defeat, and why it wasn't until Eärendil sought forgiveness of the Valar, so to speak, that Morgoth could be defeated. It wasn't until the Noldor recieve the pardon of the Valar that they were morally Right- and thus received the "help form above" that was necessary to defeat evil.