行火必有因，烟火必素具。
To use fire, some medium must be relied upon.
Equipment for setting fires must always be at hand.
发火有时，起火有日。
There are suitable times and appropriate days on which to raise fires. 'Times' means when the weather is scorching hot; 'days' means when the moon is in Sagittarius, Alpharatz, I, or Zhen constellations, for these are days of rising winds.
时者，天之燥也；日者，月在箕、壁、翼、轮也。
There are suitable times and appropriate days on which to raise fires. 'Times' means when the weather is scorching hot; 'days' means when the moon is in Sagittarius, Alpharatz, I, or Zhen constellations, for these are days of rising winds.
凡此四宿者，风起之日也。
Now, in fire attacks, one must respond to the changing situation.
凡火攻，必因五火之变而应之。
When fire breaks out in the enemy's camp, immediately coordinate your action from without.
火发于内，则早应之于外。
But if the enemy troops remain calm, bide your time and do not attack at once.
火发兵静者，待而勿攻，极其火力，可从而从之，不可从而止。
When the fire reaches its height, follow up if you can.
If you cannot do so, wait.
If you can raise fires outside the enemy camp, it is not necessary to wait until they are started inside.
火可发于外，无待于内，以时发之。
Set fires at suitable times.
When fires are raised upwind, do not attack from downwind.
火发上风，无攻下风。
When the wind blows during the day, it will die down at night.
昼风久，夜风止。
When the wind blows during the day, it will die down at night.
凡军必知有五火之变，以数守之。
Now, the army must know the five different fire attack situations and wait for appropriate times.
故以火佐攻者明，以水佐攻者强。
Those who use fire to assist their attacks can achieve good results; those who use inundations produce a powerful effect.
水可以绝，不可以夺。
Water can isolate an enemy, but cannot destroy his supplies or equipment as fire can.
夫战胜攻取，而不修其功者凶，命日费留。
Now, to win battles and take your objectives but to fail to consolidate these achievements is ominous and may be described as a waste of time.
故曰：明主虑之，良将修之。
And therefore, it is said that enlightened rulers must deliberate upon the plans to go to battle, and good generals carefully execute them.
非利不动，非得不用，非危不战。
And therefore, it is said that enlightened rulers must deliberate upon the plans to go to battle, and good generals carefully execute them.
主不可以怒而兴师，将不可以温而致战。
If not in the interests of the state, do not act.
If you cannot succeed, do not use troops.
If you are not in danger, do not fight a war.
合于利而动，不合于利而止。
A sovereign cannot launch a war because he is enraged, nor can a general fight a war because he is resentful.
怒可以复喜，慢可以复悦，亡国不可以复存，死者不可以复生。
For while an angered man may again be happy, and a resentful man again be pleased, a state that has perished cannot be restored, nor can the dead be brought back to life.
Therefore, the enlightened ruler is prudent and the good general is warned against rash action.
Thus the state is kept secure and the army preserved.
故明君慎之，良将警之，此安国全军之道也。
For while an angered man may again be happy, and a resentful man again be pleased, a state that has perished cannot be restored, nor can the dead be brought back to life.
Therefore, the enlightened ruler is prudent and the good general is warned against rash action.
Thus the state is kept secure and the army preserved.