The Art of War by Sun Tzu

II Waging War

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

6. There is no instance of a country having benefited from prolonged warfare.

Notes by Zephyrist:

Sun Tzu is basically saying making war is all about timing. Don't rush into things but then again don't wait around for ever. The key to winning a battle is picking that one perfect moment when everything is to your advantage.

Prolonged warfare drains the state leaving it impoverished. Although there is something to be said for having an enemy or having competition. An emery stimulates growth and innovation in order to be better than your enemy. So while physical battle my not be good in the long term, a mental battle can sharpen your resources and innovation.