Could Gandalf have won the war alone?

[CSteefel]

There is presumably some distinction between the statement "no weapons you have could harm me..." and the ability to actually throw down Sauron, which implies something beyond self-defense. Raynor's quote of the line that "Black is mightier still..." is very much to the point.

As we have seen, you can't simply blindly apply the hierarchy of Middle Earth--Sauron has significantly increased his power, through his own talents and through the forging of the Ring, over the course of two ages of the Earth, so he is more than a match for any number of Maia. Also, this seems to run completely counter to the entire point of the book, which is that in the end Sauron will be defeated by the lesser people, who he has ignored and underestimated. His inability to understand the course of action devised by Gandalf, namely to destroy the Ring rather than to use it, is his real undoing--of course, it is Gandalf who takes advantage of this, but that isn't the same as saying that Gandalf will storm Barad Dur...