Their arrow supply was all but endless. With their excess of numbers, they could effectively lock out the Yarmdon archers permanently from the fight, no matter where they moved to.
It brought a smile to Leviticus' lips. They'd tempted them with a trap, thinking him to be weak – thinking that they could afford to lay a trap in the first place. That they'd have a chance against one thousand. One thousand soldiers weren't simply a thousand men though – they were sources of individual opportunity. He didn't need to surround the enemy to kill them, he could use his number in other ways, as he had with the archers.
