Wars, therefore, are to be undertaken for this end, that we may live in peace, without being injured; but when we obtain the victory, we must preserve those enemies who behaved without cruelty or inhumanity during the war.
So the principles of warfare are: Do not depend on the enemy not coming, but depend on our readiness against him. Do not depend on the enemy not attacking, but depend on our position that cannot be attacked.
When, however, you have an enemy, then do not requite him good for evil: for that would shame him. Instead, prove that he did some good for you. And rather be angry than put to shame! And when you are cursed, I do not like it that you want to bless. Rather curse a little also! And if you are done a great injustice, then quickly add five small ones. Hideous to behold is he who is obsessed with an injustice.
As for the virtuous poor, one can pity them, of course, but one cannot possibly admire them. They have made private terms with the enemy, and sold their birthright for very bad pottage. They must also be extraordinarily stupid.
All people should disclose whether they submit to Allah or not. Those who are against us are our enemies and must be fought. That includes people who call themselves Muslims but who don't lead their lives as such - people who drink, who don't pray, who don't fast, who have constantly changing partners and who are unable to recite the Koran.
Though fraud in all other actions be odious, yet in matters of war it is laudable and glorious, and he who overcomes his enemies by stratagem is as much to be praised as he who overcomes them by force.