7. When an army has penetrated into the heart of a hostile country, leaving a number of fortified cities in its rear, it is serious ground.
8. Mountain forests, rugged steeps, marshes and fens--all country that is hard to traverse: this is difficult ground.
9. Ground which is reached through narrow gorges, and from which we can only retire by tortuous paths, so that a small number of the enemy would suffice to crush a large body of our men: this is hemmed in ground.
10. Ground on which we can only be saved from destruction by fighting without delay, is desperate ground.