Give your enemy a chance to scape or he’ll come after you with all his might and strength.
From chapter XI, #50:
In 532 A.D., Kao Huan, afterwards Emperor and canonized as Shen-wu, was surrounded by a great army under Erh-chu Chao and others. His own force was comparatively small, consisting only of 2000 horse and something under 30,000 foot. The lines of investment had not been drawn very closely together, gaps being left at certain points. But Kao Huan, instead of trying to escape, actually made a shift to block all the remaining outlets himself by driving into them a number of oxen and donkeys roped together. As soon as his officers and men saw that there was nothing for it but to conquer or die, their spirits rose to an extraordinary pitch of exaltation, and they charged with such desperate ferocity that the opposing ranks broke and crumbled under their onslaught.