Xenophon, Cyropaedia
Walter Miller, Ed.

Now the enemy on their part, when they saw the Medes advance, halted, some with spears poised, others with bows drawn, expecting that the other side would also halt, as soon as they came within bow-shot, just as they were accustomed generally to do; for it was their habit to advance only so far against each other, when they came into closest quarters, and to skirmish with missiles, oftentimes till evening. But when they saw their comrades rushing in flight toward them, and Cyrus and his followers bearing down close upon them, and Astyages with his cavalry getting already within bow-shot, they broke and fled with all their might from the Medes who followed hard after them.

The Medes caught up with many of them; and those whom they overtook they smote, both men and horses; and the fallen they slew. Nor did they stop, until they came up with the Assyrian infantry. Then, however, fearing lest some greater force might be lying in ambush, they came to a halt.