What if Gandalf the White killed the Witch King?

[Zigûr]

Originally Posted by Moonraker

But would anyone within the Mordor ranks seriously be in a position to risk confronting Gandalf the White in full flow at the main gate of Minas Tirith, having seen their great commander slain before them? I can't see it myself, even Gothmog would be at a loss.

Why is "confronting" Gandalf an issue? Aren't we just talking about who would command the army?

Originally Posted by Moonraker

They may well have needed Sauron to make an appearance to restore belief again.

I doubt it. Sauron's armies were led by the will of Sauron himself, by fear of their masters and hatred of their enemies. I don't see the Lord of the Nazgûl's leadership as being one of inspiration without which the hosts of Mordor were in disarrary. See Morgoth's Ring for the following regarding Sauron: "the Orcs of his own trained armies were so completely under his will that they would sacrifice themselves without hesitation at his command. And he proved even more skilful than his Master also in the corruption of Men who were beyond the reach of the Wise, and in reducing them to a vassalage, in which they would march with the Orcs, and vie with them in cruelty and destruction."
So evidently Sauron's armies could very much be led by 'remote control' as it were, and the Easterlings and Haradrim would follow suit.

Originally Posted by Moonraker

The Mouth of Sauron isn't as powerful as the Witch King, so I am not sure what he would bring to the battle scene other than a token of leadership and urgency to proceedings. Incidenally, what happened to the Mouth of Sauron once the Ring was destroyed?

Well he would in all likelihood have been in Barad-dûr during the Battle of the Pelennor Fields anyway, wouldn't he? So I don't see how him "bringing something" to the battle is even an issue. After the Ring was destroyed one assumes he was killed in the upheavals, but in any event it's a non-issue. He ceased to be important and we never hear about him again.

Originally Posted by Moonraker

The Mumakil would have been unfazed, however, and would make no bones about attacking the main gate, But the archers of Minas Tirith would have a field day at targeting the eyes of these monsters, ultimately leading to their carcasses blocking the gate.

If you say so, but really your guess is as good as anyone else's unless there is textual evidence to back up these kinds of assertions.