"Peace" is the most common word on a Muslim's tongue. Whenever two people meet, they exchange greetings, wishing each other peace: "Peace be upon you." But peace cannot prevail except through justice. Since the concept of justice may differ from one man to another, or from one society to another, Muslims believe that real justice is that which is specified by Allah (God).Islam permits fighting in self-defense, in defense of the religion, or by those who have been expelled forcibly from their homes. At the same time, Islam requires one to treat one's enemy mercifully. It lays down strict rules of combat which include prohibitions against harming civilians and against destroying crops, trees, and livestock. Islam also requires that if an enemy declares his desire to end hostilities and seek peace, the Muslims must do the same.
The concept of Jihad (struggling in the cause of Allah) is stated in the Qur'an. Allah said: "Fight in the cause of God those who fight you, but do not transgress limits. God does not love transgressors." [2:19] Jihad is never to be waged to force anybody to choose a particular religion. On the contrary, it is to waged to protect his right to choose freely. Therefore, if there is a force in the world that tries to prevent a person from practicing this right, Jihad may lead to fighting the force that is trying to prevent him from exercising free will.