Helaman has supposed correctly that the Lamanites had turned to fight. The battle was not going well for Antipus and his men. Antipus himself had fallen, and the loss of a leader in battle would have been particularly disheartening. Combined with their fatigue from marching even faster to force the Lamanites to turn from Helaman’s two thousand, they were in even worse straits.
Before describing the battle, Helaman tells Mormon what the outcome was: “had I not returned with my two thousand they would have obtained their purpose.” The Lamanites would have won, but they didn’t.