4. 夫鈍兵挫銳屈力殫貨則諸侯乘其幣而起雖有智者不能善其後矣
5. 故兵聞拙速未睹巧之久也

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.

Following Tu Yu, I understand 善 in the sense of “to make good,” i.e. to mend. But Tu Mu and Ho Shih explain it as “to make good plans” — for the future.

5. Thus, though we have heard of stupid haste in war, cleverness has never been seen associated with long delays.