4. Now, when your weapons are dulled, your ardour damped, your strength exhausted and your treasure spent, other chieftains will spring up to take advantage of your extremity. Then no man, however wise, will be able to avert the consequences that must ensue.
5. Thus, though we have heard of stupid haste in war, cleverness has never been seen associated with long delays.
[This concise and difficult sentence is not well explained by any of the commentators. Ts’ao Kung, Li Ch’uan, Meng Shih, Tu Yu, Tu Mu and Mei Yao-ch’en have notes to the effect that a general, though naturally stupid, may nevertheless conquer through sheer force of rapidity. Ho Shih says: "Haste may be stupid, but at any rate it saves expenditure of energy and treasure; protracted operations may be very clever, but they bring calamity in their train." Wang Hsi evades the difficulty by remarking: "Lengthy operations mean an army growing old, wealth being expended, an empty exchequer and distress among the people; true cleverness insures against the occurrence of such calamities." Chang Yu says: "So long as victory can be attained, stupid haste is preferable to clever dilatoriness." Now Sun Tzŭ says nothing whatever, except possibly by implication, about ill-considered haste being better than ingenious but lengthy operations. What he does say is something much more guarded, namely that, while speed may sometimes be injudicious, tardiness can never be anything but foolish—if only because it means impoverishment to the nation. In considering the point raised here by Sun Tzŭ, the classic example of Fabius Cunctator will inevitably occur to the mind. That general deliberately measured the endurance of Rome against that of Hannibals’s isolated army, because it seemed to him that the latter was more likely to suffer from a long campaign in a strange country. But it is quite a moot question whether his tactics would have proved successful in the long run. Their reversal it is true, led to Cannae; but this only establishes a negative presumption in their favour.]
6. There is no instance of a country having benefited from prolonged warfare.
7. It is only one who is thoroughly acquainted with the evils of war that can thoroughly understand the profitable way of carrying it on.
[That is, with rapidity. Only one who knows the disastrous effects of a long war can realize the supreme importance of rapidity in bringing it to a close. Only two commentators seem to favour this interpretation, but it fits well into the logic of the context, whereas the rendering, "He who does not know the evils of war cannot appreciate its benefits," is distinctly pointless.]
8. The skilful soldier does not raise a second levy, neither are his supply-waggons loaded more than twice.
[Once war is declared, he will not waste precious time in waiting for reinforcements, nor will he return his army back for fresh supplies, but crosses the enemy’s frontier without delay. This may seem an audacious policy to recommend, but with all great strategists, from Julius Caesar to Napoleon Bonaparte, the value of time—that is, being a little ahead of your opponent—has counted for more than either numerical superiority or the nicest calculations with regard to commissariat.]
9. Bring war material with you from home, but forage on the enemy. Thus the army will have food enough for its needs.
[The Chinese word translated here as "war material" literally means "things to be used", and is meant in the widest sense. It includes all the impedimenta of an army, apart from provisions.]