Battle Casualties in the Ancient World
…Taken together the data [on ancient battles] suggest that seven of every ten soldiers of the defeated force would become casualties by day’s end. About one-third of the force would be killed and another third wounded severely enough to be left behind to die or shift for themselves on the battlefield. The victors could expect to lose to enemy arms approximately one in every ten men, either killed or wounded.
— From Sumer To Rome, p. 88