The Northern Di

The Northern Di dwell without city walls; they follow the water and grass in migration. When circumstances favor them, they invade southward; when circumstances fail them, they flee northward. Long mountains and vast deserts are sufficient for them to protect themselves. When hungry, they hunt beasts and drink milk; when cold, they sleep on hides and wear fur. They run about shooting and hunting, taking killing as their business. They cannot be won over by morality, nor subdued by arms. The Han do not fight them directly, for three reasons. First, Han soldiers both farm and fight, and are therefore exhausted and timid; the enemy only herds and hunts, and is therefore at ease and brave. To oppose exhaustion with ease, timidity with bravery, is not a match—this is the first reason not to fight. Second, the Han excel in walking, covering a hundred li a day; the enemy excel in riding, covering several times that in a day. When the Han pursue the enemy, they must carry grain and armor with them; when the enemy pursue the Han, they drive fast horses to transport their......