The Attack by Fire

Each target compounds the harm — destroying supply and shelter cripples a force more lastingly than killing men in the field, because an army without provisions, equipment, or a base is already defeated.

Fire, however, is not a tool of impulse; it demands preparation and timing. "There is a proper season for making attacks with fire, and special days for starting a conflagration." The proper season is when the weather is very dry; the special days are those when the moon is in certain constellations, "for these are days of rising wind." The commander must have the materials ready in advance — fire cannot be improvised.

He then lays out responses keyed to how a fire develops. When fire breaks out inside the enemy's camp, answer at once with an attack from without. If the soldiers remain quiet despite the fire, bide your time and do not attack — wait until the blaze reaches its height, then follow up if you can, hold back if you cannot. If you can raise fire from outside, do not wait for it to break out within; start it at the right moment. When the fire is on the windward side, do not attack from the leeward; a wind that rises by day lasts, but a night breeze soon falls. "In every army, the five developments connected with fire must be known," and the commander must watch the days and stay on guard.

Sun Tzu contrasts fire with water. Those who use fire to aid an attack show intelligence; those who use water show strength. "Water can intercept and isolate an enemy, but it cannot deprive him of all his belongings" the way fire can. Water divides; fire destroys.

The chapter then widens into a sober warning that reads as the book's moral center. The truly dangerous failure, he says, is to win battles and conquests but fail to consolidate the gains — wasted effort and lost time. So "the enlightened ruler lays his plans well ahead; the good general cultivates his resources." And then the famous restraint: "Move not unless you see an advantage; use not your troops unless there is something to be gained; fight not unless the position is critical." No ruler should put troops into the field merely to gratify his own spleen; no general should fight a battle simply out of pique. "If it is to your advantage, make a forward move; if not, stay where you are. Anger may in time change to gladness; vexation may be succeeded by content. But a kingdom that has once been destroyed can never come again into being; nor can the dead ever be brought back to life." The chapter ends with its quiet thesis: "Hence the enlightened ruler is heedful, and the good general full of caution. This is the way to keep a country at peace and an army intact." The destructive power that opens the chapter is precisely why it closes on caution — the more devastating the weapon, the more disciplined the decision to use it must be.