Arrian

They, astounded at the flash of the armor, and the swiftness of the charge, and attacked by showers of arrows and missiles, half naked as they were, never stopped to resist but gave way.

Our enemies are Medes and Persians, men who for centuries have lived soft and luxurious lives; we of Macedon for generations past have been trained in the hard school of danger and war. Above all, we are free men, and they are slaves.

They must therefore not spoil Alexander's undertaking, especially when they were almost at the close of their toils, and were, moreover, no longer in any difficulty about provisions on their coasting cruise.