Waging War

Chapter 2 opens with an accounting of scale. A major military operation requires thousands of chariots, hundreds of thousands of armored soldiers, supply trains stretching hundreds of miles — and the cost falls on households at home through conscription, requisitioning, and the disruption of agriculture. When victory takes too long, troops grow weary, morale collapses, weapons grow blunt, and the treasury empties. When the treasury empties, rival powers move in on the weakened state. Speed in war may sometimes be clumsy, Sun Tzu says, but no one has ever seen brilliance come from dragging things out.

The practical doctrine follows. A skilled commander does not conscript troops twice or resupply more than once. Bring equipment from home, but take food from the enemy — that way the army never goes hungry. One cartload of the enemy's provisions is worth twenty of your own, because of the cost of moving supplies over long distances. To motivate soldiers to kill the enemy, you must stoke their fighting spirit; to motivate them to seize the enemy's resources, reward those who do so first. Replace the enemy's flags with your own; integrate captured chariots into your formation; treat prisoners well and use them.

The chapter closes with the general principle: in war, pursue decisive victory — not drawn-out campaigns. The commander holds the fate of the people in his hands. He determines whether the nation lives in peace or falls into decline. The calculation of Chapter 2 is the premise of the doctrine that runs through the rest of the book: because war costs so much, the general's first obligation is to win it as quickly and as cheaply as possible, and the surest path to that is the intelligence and preparation that make the battle short.