The Nazgul at Weathertop
Paul B.

I don't believe the Nazgul retreated at Weathertop in any sense of defeat. They fall back because they believe their goal for the attack - the stabbing of Frodo with a Morgul-knife - has been achieved. The effects of this, Gandalf tells Frodo in Rivendell, would have been to make Frodo a wraith, 'only weaker and under their [the Nazgul's] command.' Remember that Frodo hesitates when Glorfindel tells him to fly at the Ford - he can he hear the Ring-wraiths calling. He can even see them without having to put on the Ring. They do not have to take the Ring, he will bring it to them. The reason the Weathertop attack fails is because the Ring-wraiths (and Sauron) under-estimated the resilience of a hobbit to a Morgul-knife. Gandalf states that he knows of 'strong warriors of the Big People who would quickly have been overcome'. The expectation was that Frodo would succumb in a few days, a week at very most. Yet he carries around a splinter in his shoulder for nearly three weeks!

As for the use of the word 'Elbereth' Aragorn states that the name is deadly (though I suspect not in the literal sense!) to the Witch-king. It is interesting to note that on Weathertop Frodo calls out 'O Elbereth! Gilthoniel!', whereas at the the ford he says 'By Elbereth and Luthien the Fair you shall have neither the Ring nor me'. Any eleven-lore/language experts know the different effects that these two phrases might have?

Aaron, where does Gandalf state that the witch-king was not at Weathertop. It seems fairly certain from the description of the Nazgul who stabs Frodo ('and on his helm was a crown') that this was indeed the Witch-king. The next morning Aragorn refers to that 'dreadful King'. And, at the Council of Elrond Gandalf states that after his fight with the Nazgul on October 3rd he manages to draw off four of them, though they broke off pursuit and instead headed for the ford. For this reason the Hobbits and Strider only have to face five of the nine. Gandalf does not however elaborate on the identities of the four who chased him.

I think it highly unlikely that the Witch-king feared one of the Nazgul taking the Ring for himself. For one thing, if there had been any possiblity that any of the Nazgul could desire and take the One Ring for himself, I doubt Sauron would have sent them. In any case this is completely impossible. The Ringwraiths wear their nine rings (for mortal men doomed to die) and are thus under the complete dominion of the One Ring. One Ring to rule them all?