The Battle of the river Xerias was a classic clash between two phalanxes. As was not uncommon in Greek warfare, the battle was decided on the wings, where the Achaeans routed the enemy flank. But Aratus, leading the other wing, was injured, and he pulled back. To the outrage of the Achaeans on the victorious wing, this allowed Aristippus to claim victory. The next day, after lining up his army again for battle, Aratus decided to retreat on seeing that the enemy had gained numerical superiority through reinforcements.