If fighting is sure to result in victory, then you must fight, even if the ruler forbids it. If fighting will not result in victory, then you must not fight even at the ruler’s bidding. The general who advances without coveting fame and retreats without fearing disgrace, whose only thought is to protect his country and do good service for his sovereign, is the jewel of the kingdom. There are five dangerous faults which may affect a general: (1) Recklessness, which leads to destruction, (2) cowardice, which leads to capture, (3) a hasty temper, which can be provoked by insults; (4) a delicacy of honour which is sensitive to shame and (5) over-solicitude for his men, which exposes him to worry and trouble.
A summary of the book can be read here.