I don't have my books so I can't reference it for sure.
I guess it could be like a standing order not to let anyone across or it could be directed at this group, but do either of the evil minds know for sure what is up with the fellowship at this time?
...`We cannot go further tonight,' said Boromir. `Let those call it the wind who will; there are fell voices on the air; and these stones are aimed at us.'`I do call it the wind,' said Aragorn. `But that does not make what you say untrue. There are many evil and unfriendly things in the world that have little love for those that go on two legs, and yet are not in league with Sauron, but have purposes of their own. Some have been in this world longer than he.'
'Caradhras was called the Cruel, and had an ill name, said Gimli, `long years ago, when rumour of Sauron had not been heard in these lands.'
`It matters little who is the enemy, if we cannot beat off his attack; said Gandalf...
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`Ah, it is as I said,' growled Gimli. 'It was no ordinary storm. It is the ill will of Caradhras. He does not love Elves and Dwarves, and that drift was laid to cut off our escape.'
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`Enough, enough!' cried Gimli. 'We are departing as quickly as we may!' And indeed with that last stroke the malice of the mountain seemed to be expended, as if Caradhras was satisfied that the invaders had been beaten off and would not dare to return. The threat of snow lifted; the clouds began to break and the light grew broader.
As Legolas had reported, they found that the snow became steadily more shallow as they went down, so that even the hobbits could trudge along. Soon they all stood once more on the flat shelf at the head of the steep slope where they had felt the first flakes of snow the night before.
The morning was now far advanced. From the high place they looked back westwards over the lower lands. Far away in the tumble of country that lay at the foot of the mountain was the dell from which they had started to climb the pass.
Frodo's legs ached. He was chilled to the bone and hungry; and his head was dizzy as he thought of the long and painful march downhill. Black specks swam before his eyes. He rubbed them, but the black specks remained. In the distance below him, but still high above the lower foothills, dark dots were circling in the air.
`The birds again!' said Aragorn, pointing down.
'That cannot be helped now,' said Gandalf. `Whether they are good or evil, or have nothing to do with us at all, we must go down at once. Not even on the knees of Caradhras will we wait for another night-fall!'
A cold wind flowed down behind them, as they turned their backs on the Redhorn Gate, and stumbled wearily down the slope. Caradhras had defeated them.