In peace prepare for war, in war prepare for peace. The art of war is of vital importance to the state. It is matter of life and death, a road either to safety or to ruin. Hence under no circumstances can it be neglected.
He who wishes to fight must first count the cost. When you engage in actual fighting, if victory is long in coming, then men's weapons will grow dull and their ardor will be dampened. If you lay siege to a town, you will exhaust your strength.