In the book, the battle covers much less than the film does. This is because
Peter Jackson chose to emphasize characters that needed things to do in the
film. However, the elves did not actually come to the rescue in the book.
Instead, the men of Rohan, along with Aragorn, Legolas, and Gimli, fended off
the orcs until day break, when the men of the Rohirrim arrived with Gandalf.
Then the trees of Fangorn also arrived and completely annihilated what was left
of the orcish horde. There were archers used in the battle, but they did not
belong to the
elves.
