
When it was to their advantage, they made a forward move when otherwise, they stopped still.

When the enemy's men were united, they managed to keep them in disorder. Those who were called skillful leaders of old knew how to drive a wedge between the enemy's front and rear to prevent co-operation between his large and small divisions to hinder the good troops from rescuing the bad, the officers from rallying their men. On hemmed-in ground, resort to stratagem. In difficult ground, keep steadily on the march. On the ground of intersecting highways, join hands with your allies. On open ground, do not try to block the enemy's way. On dispersive ground, therefore, fight not. Ground on which we can only be saved from destruction by fighting without delay, is desperate ground. 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. Mountain forests, rugged steeps, marshes and fens-all country that is hard to traverse: this is difficult ground. 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. Ground which forms the key to three contiguous states, so that he who occupies it first has most of the Empire at his command, is a ground of intersecting highways. Ground on which each side has liberty of movement is open ground. Ground the possession of which imports great advantage to either side, is contentious ground.

When he has penetrated into hostile territory, but to no great distance, it is facile ground. When a chieftain is fighting in his own territory, it is dispersive ground. Sun Tzu said: The art of war recognizes nine varieties of ground:
