When the Elves came under attack by the demons in "The Elfstones of Shannara", he was given the command of the army preparing to defend Worl Run that was to attempt to stop the demons from flanking them.
He was given the command of the army. This army was preparing to defend Worl Run. This Worl Run was to attempt to stop the demons from flanking them. The Elves came under attack by the demons in "The Elfstones of Shannara".