[narfforc]

I have always felt that Gandalf does defeat Sauron, and The Witch-king for that matter. It is not by outward blasts of power that he achieves this, it is by wisdom, foresight and being one step ahead of the game. Gandalf releases Theoden from the grip of Saruman therefore allowing the Rohirrim to turn up at The Battle of The Pelennor Fields just in time, and it is Gandalf who convinces Elrond to allow the two youngers hobbits to be part of The Fellowship therefore allowing Merry to be present during Eowyns battle with The Witch-king, if not for Gandalf being the prime mover of the forces of good, then the scene at the Gates of Minas Tirith may have been different. Gandalf achieves the prime directive by wisdom and not by the power of force, this was his mission, not to oppose Sauron by way of Power.