In rides the Lord of the Nazgul! A great black shape against the fires beyond he looms up, grown to a vast menace of despair. In rides the Lord of the Nazgul, under the archway that no enemy ever yet had passed, and all flee before his face!
And Tolkein for his part saw WW1 in the trenches. As
@minow said once in a different thread:
'In regards to fear, I'd just like to note that Tolkien served on the front lines in WWI. I've no doubt he had a rather mature and deep understanding of fear in its varied ways, and when he wrote that someone was without fear, I expect that he meant they were utterly without fear, not the sort of "I'm afraid but my courage overcomes it" that any combat soldier has probably experienced. Where you place Eowyn's "faithful beyond fear" on this scale might be a matter of some debate, but surely when a man who lived through (and didn't run from) front-lines combat in WWI writes something as so scary that battle-hardened soldiers simply flee from it, he means it to be really fucking scary.'
It's no exaggeration that Tolkien saw almost every single one of his close friends from childhood die in the War. Many have noted how the defenders along the walls behave like victims of what was then understood as shell-shock. You can quibble as hard as you like, but Tolkien depicts the fear the Nine projected at the Gladden Fields as not just a base animal fear, but a
despair beyond mortal writ to withstand from deeply personal experience. The only mortal not of Numenorean or Elven constitution to actually stand without the presence of one who could shield them from their influence was someone
who wanted with the fullness of hope to die a self-made martyr.
When the Witch King entered through the ruined gates of the once impregnable city,
only Gandalf was there to meet him.
I don't think the importance of this factor can be overestimated. It's pretty clear that no mortal men not in the possession of divine grace could resist the terror of the Nine its height. However, I think there's something rather interesting here that may have been missed.
To start off with, we need to go back to basics. Tolkien was a deeply devout Catholic. In Middle Earth's legendarium he wanted to create a mythic prehistory of the world which was still consistent with Christian and in particular Catholic teaching. He was vastly more subtle (and proportionately more effective) at doing this than his friend C.S. Lewis, but it's still pretty straightforward. Eru is the Christian God, not just figuratively, but literally, and the same goes for Morgoth as Lucifer. There is even an origin story of humanity in Middle Earth, the
Tale of Adanel, which Tolkien only hinted at in the
Silmarillion but is provided in full in one of the volumes of his collected writings. This is essentially the Eden story but with tribes of humans instead of Adam and Eve, and Morgoth as the Serpent, and Original Sin taking the form of humans being seduced by Morgoth's and eventually worshipping him in place of Eru, before some (the ancestors of the heroic Edain of the First Age who gave rise to the Númenóreans) repented.
We can also see the Christian theology underpinning Middle Earth reflected in the veneration that the Elves and more noble men give to Eru. They venerate him, but they have no organized religion because they predate even Abraham by eons, and positing an organized Abrahamic religion
before Abraham would be deeply blasphemous! (In fact, the Noldor and Numenoreans predate the Flood, which may or may not in Middle Earth be the same thing as the Downfall of Númenor.) Indeed, Tolkien himself reckoned that the Fall of Barad-Dur was roughly six thousand years distant from modern days, putting the twentieth century
somewhere between the Fifth to Seventh Age depending on how it is reckoned. As far as Tolkien would be concerned if you asked him, the War of the Ring was not a fantasy story to the Union soldiers,
it is an event which happened in their ancient past.
Now it's worth asking the question, did anything significant occur in the intervening millennia between Sauron's downfall and the American Civil War?
To a devout Christian like Tolkien, the most important event in history happened in that time. It is an event which means every Union soldier, especially the faithful amongst them, carries with them a grace that even Elendil or the mightiest amongst the Elves did not possess. It is a grace which means that the terror of the Nazgûl, which is but merely the faded after-echo of that terrible fear and darkness which pursued the first Men who fled out of Hildórien, may frighten and alarm the Union soldiers, but
cannot rob them of their wills. Their hearts have been vouchsafed by another, a king even mightier than Melkor or Manwë Súlimo.
They have been Washed in the Blood of the Lamb.
