Regard well the developments that will certainly arise from the fire, and act upon them. When fire breaks out inside the enemy's camp, thrust upon him with all speed from without; but if his soldiers be quiet, wait, and do not attack. When the fire is at its height, attack or not, as opportunity may arise. If the opportunity be favourable, set fire to the enemy's camp, and do not wait for it to break out from within. When fire breaks out on the windward side, do not attack from the leeward. Wind that rises in the day lasts long. Wind that rises in the night time quickly passes away. The peculiarities of the five burnings must be known, and the calendar studied, and, if the attack is to be assisted, the fire must be unquenchable. If water is to assist the attack, the flood must be overwhelming. Water may isolate or divide the enemy; fire may consume his camp; but unless victory or possession be obtained, the enemy quickly recovers, and misfortunes arise. The war drags on, and money is spent. Let the enlightened lord consider well; and the good general keep the main object in view. If no advantage is to be gained thereby, do not move; without prospect of victory, do not use the soldiers; do not fight unless the state be in danger. War should not be undertaken because the lord is in a moment of passion. The general must not fight because there is anger in his heart. Do not make war unless victory may be gained thereby; if there be prospect of victory, move; if there be no prospect, do not move. For passion may change to gladness, anger passes away; but a country, once overturned, cannot be restored; the dead cannot be brought to life. Wherefore it is written, the enlightened lord is circumspect, and the good general takes heed; then is the state secure, and the army victorious in battle. XIII THE EMPLOYMENT OF SPIES Sun the Master said:-- Calling 100,000 men to arms, and transporting them a hundred leagues, is such an undertaking that in one day 1,000 taels of the citizens' and nobles' money are spent; commotions arise within and without the state; carriers fall down exhausted on the line of march of the army; and the occupations of 700,000[14] homes are upset. Again, for years the armies may face each other; yet the issue may depend on a single day's victory. Wherefore, by grudging slight expense in titles and salaries to spies, to remain in ignorance of the enemy's circumstances, is to be without humanity. Such a person is no general; he is no assistance to his lord; he is no master of victory. The enlightened ruler and the wise general who act, win, and are distinguished beyond the common, are informed beforehand. This knowledge is not to be got by calling on gods and demons; nor does it come of past experience nor calculation. It is through men that knowledge of the enemy is gained. Now the five kinds of spies are these: village spies, inner spies, converted spies, death spies, living spies.