Chang Yü relates the following anecdote of Kao Tsu, the first Han Emperor: “Wishing to crush the Hsiung-nu, he sent out spies to report on their condition. But the Hsiung-nu, forewarned, carefully concealed all their able-bodied men and well-fed horses, and only allowed infirm soldiers and emaciated cattle to be seen. The result was that the spies one and all recommended the Emperor to deliver his attack.” 婁敬 Lou Ching alone opposed them, saying: “When two countries go to war, they are naturally inclined to make an ostentatious display of their strength. Yet our spies have seen nothing but old age and infirmity. This is surely some _ruse_ on the part of the enemy, and it would be unwise for us to attack.” The Emperor, however, disregarding this advice, fell into the trap and found himself surrounded at 白登 Po-têng.” 19. 故善動敵者形之敵必從之予之敵必取之 Thus one who is skilful at keeping the enemy on the move maintains deceitful appearances, according to which the enemy will act. Ts‘ao Kung’s note is 見羸形也 “Make a display of weakness and want,” but Tu Mu rightly points out that 形 does not refer only to weakness: “If our force happens to be superior to the enemy’s, weakness may be simulated in order to lure him on; but if inferior, he must be led to believe that we are strong, in order that he may keep off. In fact, all the enemy’s movements should be determined by the signs that we choose to give him.” The following anecdote of 孫臏 Sun Pin, a descendant of Sun Wu, is related at length in the 史記, chap. 65: In 341 B.C., the 齊 Ch‘i State being at war with 魏 Wei, sent 田忌 T‘ien Chi and Sun Pin against the general 龐涓 P‘ang Chüan, who happened to be a deadly personal enemy of the latter. Sun Pin said: “The Ch‘i State has a reputation for cowardice, and therefore our adversary despises us. Let us turn this circumstance to account.” Accordingly, when the army had crossed the border into Wei territory, he gave orders to show 100,000 fires on the first night, 50,000 on the next, and the night after only 20,000. P‘ang Chüan pursued them hotly, saying to himself: “I knew these men of Ch‘i were cowards: their numbers have already fallen away by more than half.” In his retreat, Sun Pin came to a narrow defile, which he calculated that his pursuers would reach after dark. Here he had a tree stripped of its bark, and inscribed upon it the words: “Under this tree shall P‘ang Chüan die.” Then, as night began to fall, he placed a strong body of archers in ambush near by, with orders to shoot directly they saw a light. Later on, P‘ang Chüan arrived at the spot, and noticing the tree, struck a light in order to read what was written on it. His body was immediately riddled by a volley of arrows, and his whole army thrown into confusion. [The above is Tu Mu’s version of the story; the _Shih Chi_, less dramatically but probably with more historical truth, makes P‘ang Chüan cut his own