Crassus now hoped that his legionaries could hold out until the Parthians ran out of arrows. However, Surena used thousands of camels to resupply his horse archers. Upon realizing this, Crassus dispatched his son Publius with 1,300 Gallic cavalry to drive off the horse archers. The horse archers retreated, and after suffering heavy casualties from arrow fire, his cavalry were confronted by the Parthian cataphracts. The horse archers outflanked the Gauls and cut off their retreat. Publius and his men were slaughtered. Crassus, unaware of his son's fate but realizing Publius was in danger, ordered a general advance. He was confronted with the sight of his son's head on a spear. The Parthian horse archers began to surround the Roman infantry, shooting at them from all directions, while the cataphracts mounted a series of charges that disorganized the Romans. The Parthian onslaught did not cease until nightfall...
http://en.wikipedia.org/wiki/Battle_of_Carrhae#The_battle
