So what's up with Nazgûl and their mounts?

[caedmon]

Reading Fellowship again, and got to the part where Legolas kills the fell beast at the river. And it occurred to me that the Nazgûl's mounts seem to be integral to their ability to be in the world.


Why did the death of their horses matter at the Ford of Bruinen? Why couldn't the Nazgûl just keep going? Why did the Nazgûl on the fell beast not simply keep pursuing the Fellowship, it's not more that a bow shot away. And the Anduin isn't some Elf-lord protected boundary. Did the fact that Eowyn killed the Witch King's fell beast first have any diminishing affect of him?

[Udwin]

Ooh, good observation.
I forget where--somewhere in the later half of Book 1 or first couple chapters of Book 2-- but there's one point where either Aragorn or Gandalf tells the hobbits, or else it's heavily implied that while the nazgul can't see well during the day, they essentially see 'through' the eyes of their horses. How that relates to the winged mounts and the 'upgraded' nature of the nazgul in the later books (possibly having something to do with the proximity to Mordor?) is unknown.

Where it gets weird is how getting unmounted and "discomfitted" (aka disrobed) in the Ford apparently required them to return to mordor to get re-cloaked. ??

[Turgolanas]

I always thought it was something like their essence got a bit scattered, so they had to respawn where their power was strongest, or something like that. If I remember correctly, Book Nazgûl were more limited in their ability to affect the real world than movie Nazgul, so losing horses would be a big blow to mobility. It could also be possible that the cloaks bound their spirits better to the mortal plane, or something like that?

[Eofor]

Why did the death of their horses matter at the Ford of Bruinen? Why couldn't the Nazgûl just keep going?

I don't think it was the loss of the horses that stopped them but rather the fact that the ring had passed under the protection of Elrond. If they had a large army nearby then perhaps they may have regrouped and tried to assault the valley but the nine couldn't hope to enter the valley with any chance of retrieving the ring.



Beyond that is the simple fact that they need specially trained mounts. They can't go and steal a new horse due to the aura of terror they have so they're effectively limited to whatever passes for normal movement to a Nazgul. They would still make for an implacable pursuer not needing to sleep or rest but hardly effective against mounted prey.
I suspect that is the same reason the dismounted winged Nazgul doesn't persist. He's on foot trying to keep pace with boats on a fast flowing river. All this of course raises the question of just how they return to Sauron?