Actually my 160 heavy peltasts were caught as they withdrew by the Companion Cavalry, and lasted quite a long time in melee, killing half the enemy horsemen. But when my 240 light skirmishers tried to help, they didn't last two minutes before routing off the field like girls.

My highly-experienced Kretan archers, (only a half-sized unit due to previous losses) considering themselves to be mercenaries, decided that they weren't being paid enough to die in a hopeless melee battle against enemy cavalry, and withdrew to fight another day. The slingers, also out of ammo, followed the Kretans' lead.