9. The Army on the March

21

Movement amongst the trees of a forest shows that the enemy is advancing.

Ts`ao Kung explains this as "felling trees to clear a passage," and Chang Yu says: "Every man sends out scouts to climb high places and observe the enemy. If a scout sees that the trees of a forest are moving and shaking, he may know that they are being cut down to clear a passage for the enemy's march."

The appearance of a number of screens in the midst of thick grass means that the enemy wants to make us suspicious.

Tu Yu's explanation, borrowed from Ts`ao Kung's, is as follows: "The presence of a number of screens or sheds in the midst of thick vegetation is a sure sign that the enemy has fled and, fearing pursuit, has constructed these hiding-places in order to make us suspect an ambush." It appears that these "screens" were hastily knotted together out of any long grass which the retreating enemy happened to come across.