The original text omits 藏, which has been restored from the _T‘ung Tien_ and _Yü Lan_. The _T‘u Shu_ omits 處 as well, making 所 a substantive. On 姦 Chang Yü has the note: 又慮姦細潛隱覘我虛實聽我號令 伏姦當爲兩事 “We must also be on our guard against traitors who may lie in close covert, secretly spying out our weaknesses and overhearing our instructions. _Fu_ and _chien_ are to be taken separately.” 18. 敵近而靜者恃其險也 When the enemy is close at hand and remains quiet, he is relying on the natural strength of his position. Here begin Sun Tzŭ’s remarks on the reading of signs, much of which is so good that it could almost be included in a modern manual like Gen. Baden-Powell’s “Aids to Scouting.” 19. 遠而挑戰者欲人之進也 When he keeps aloof and tries to provoke a battle, he is anxious for the other side to advance. Probably because we are in a strong position from which he wishes to dislodge us. “If he came close up to us,” says Tu Mu, “and tried to force a battle, he would seem to despise us, and there would be less probability of our responding to the challenge.” 20. 其所居者易利也 If his place of encampment is easy of access, he is tendering a bait. 易 is here the opposite of 險 in § 18. The reading of the _T‘ung Tien_ and _Yü Lan_, 其所處者居易利也, is pretty obviously corrupt. The original text, which transposes 易 and 者, may very possibly be right. Tu Mu tells us that there is yet another reading: 士爭其所居者易利也. 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.