"For more than 1,000 years the aristocratic charioteer was the arbiter of battle all over the world. Then, during the fourth century BC army formations similar to the ancient style of Egypt appeared in an infinitely more formidable guise—the legions of Rome. It was not long before the pendulum had swung and the legions swept everything before them, and for the next 600 years the Roman infantry was almost the only military force to be reckoned with in the civilized world. Even so, behind her northern and eastern frontiers were many nations of unsubdued barbarians...These nations were the force which eventually swung the pendulum back; they flooded into the Empire, not with chariots as of old, but as heavy cavalry. The weapon of impact had come into its own again, and would be the dominant force in the world until the English cloth-yard arrow began to weaken it during the fourteenth century; it finally gave way when the perfection of gunpowder in the fifteenth century brought in its turn another concept of war."