Attack by Fire — Chapter Twelve

Sun Tzu said: In all there are five kinds of fire attack: first, fire against the people; second, fire on stores; third, fire on wagons; fourth, fire on magazines; fifth, fire on the troops. To employ fire one must have a cause; smoke and flames must be properly prepared. There is a season to set fire, and there are days on which to kindle it. 'Season' means dry weather. 'Day' means when the moon is in the constellations Ji, Bi, Yi, or Zhen. On the days of these four lunar mansions, winds arise.

In any fire attack, one must respond according to the five variations of fire: if fire breaks out inside, then respond early from without; if fire breaks out and the enemy troops remain calm, wait and do not attack; when the fire reaches its peak, one may follow and exploit it; if one cannot follow, then stop. Fire can be started from outside without waiting for an internal blaze—start it at the proper time. If the fire is upwind, do not attack downwind. A long daytime wind will often cease at night. Every army must know the five changes of fire and guard against them accordingly. Thus to use fire in support of an attack is a clear tactic; to use water in support is a strong measure. Water can cut off, but it cannot seize.

When one wins in battle and seizes the prize but does not consolidate the achievement, the result is harmful; this is called 'wasteful lingering.' Therefore an enlightened ruler considers it carefully, and a good general finishes the work. Do not move without advantage, do not employ forces without gain, do not engage unless there is peril. A ruler must not raise troops in anger; a commander must not bring on battle out of resentment. Act when it is advantageous; desist when it is not. Anger can return to joy, resentment can return to pleasure, but a fallen state cannot be restored and the dead cannot be brought back to life. Therefore the wise ruler is cautious and the good general is vigilant—this is the way to secure the state and preserve the army.