According to Islamic law, the world is divided into three parts: dar al-harb (the house of war), dar al-islam (the house of Islam), and dar al-‘ahd (the house of accord); that is, the countries with which a treaty was stipulated. [...]

As for the countries belonging to the “house of war,” Islamic canon law recognizes no relations with them other than “holy war” (jihad), which signifies an “effort” in the way of Allah and has two meanings, both of which are equally essential and must not be dissociated, as if one could exist without the other. In its primary meaning, jihad indicates the “effort” that the Muslim must undertake to be faithful to the precepts of the Koran and so improve his “submission” (islam) to Allah; in the second, it indicates the “effort” that the Muslim must undertake to “fight in the way of Allah,” which means fighting against the infidels and spreading Islam throughout the world. Jihad is a precept of the highest importance, so much so that it is sometimes counted among the fundamental precepts of Islam, as its sixth “pillar.”

Obedience to the precept of the “holy war” explains why the history of Islam is one of unending warfare for the conquest of infidel lands. [...] In particular, all of Islamic history is dominated by the idea of the conquest of the Christian lands of Western Europe and of the Eastern Roman Empire, whose capital was Constantinople. Thus, through many centuries, Islam and Christianity faced each other in terrible battles, which led on one side to the conquest of Constantinople (1453), Bulgaria, and Greece, and on the other, to the defeat of the Ottoman empire in the naval battle of Lepanto (1571).

But the conquering spirit of Islam did not die after Lepanto. The Islamic advance into Europe was definitively halted only in 1683, when Vienna was liberated from the Ottoman siege by the Christian armies under the command of John III Sobieski, the king of Poland. [...] In reality, for almost a thousand years Europe was under constant threat from Islam, which twice put its survival in serious danger.

Thus, in all of its history, Islam has shown a warlike face and a conquering spirit for the glory of Allah. [...] against the “idolaters” who must be given a choice: convert to Islam, or be killed. [...] As for the “people of the Book” (Christians, Jews, and “Sabeans”), Muslims must “fight them until their members pay tribute, one by one, humiliated” (Koran, Sura 9:29). [...]