21. 衆樹動者來也衆草多障者疑也
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 Yü says: “Every army 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.
Whenever the meaning of a passage happens to be somewhat elusive, Capt. Calthrop seems to consider himself justified in giving free rein to the imagination. Thus, though his text is here identical with ours, he renders the above: “Broken branches and trodden grass, as of the passing of a large host, must be regarded with suspicion.” Tu Yu’s explanation, borrowed from Ts‘ao Kung, 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.
22. 鳥起者伏也獸駭者覆也
The rising of birds in their flight is the sign of an ambuscade.
Chang Yü’s explanation is doubtless right: “When birds that are flying along in a straight line suddenly shoot upwards, it means that soldiers are in ambush at the spot beneath.”
Startled beasts indicate that a sudden attack is coming.
An example of 覆 fou4 in the meaning of “ambuscade” may be found in the Tso Chuan, 隱 9th year: 君爲三覆以待之. In the present passage, however, it is to be distinguished from 伏 just above, in that it implies onward motion on the part of the attacking force. Thus, Li Ch‘üan defines it as 不意而至, and Tu Mu as 來襲我也.