The distinction between jihad and the crusades explained

The following is a very long quotation from an even longer article that challenges the anti-Western assumptions in Ridley Scott's Kingdom of Heaven. As far as I understand, the basic point is that jihad is an essential element of Islam -- a religion that, over the next 500 hundred years conquered, then enslaveed, killed or forcibly converted Jewish and Christian communities all around the Mediterranean. In this context, the relatively short-lived Crusades -- short-lived because they encompassed two hundred years, rather than the 1,400 years of jihad -- were a response to Muslim encroachments, not a trigger:

By the time of the classical Muslim historian al-Tabari's death in 923, jihad wars had expanded the Muslim empire from Portugal to the Indian subcontinent. Subsequent Muslim conquests continued in Asia, as well as on Christian eastern European lands. The Christian kingdoms of Armenia, Byzantium, Bulgaria, Serbia, Bosnia, Herzegovina, Croatia, and Albania, in addition to parts of Poland and Hungary, were also conquered and Islamized. When the Muslim armies were stopped at the gates of Vienna in 1683, over a millennium of jihad had transpired. These tremendous military successes spawned a triumphalist jihad literature. Muslim historians recorded in detail the number of infidels slain or enslaved, the cities and villages which were pillaged, and the lands, treasure, and movable goods seized. Christian (Coptic, Armenian, Jacobite, Greek, Slav, etc.), as well as Hebrew sources, and even the scant Hindu and Buddhist writings which survived the ravages of the Muslim conquests, independently validate this narrative, and complement the Muslim perspective by providing testimonies of the suffering of the non-Muslim victims of jihad wars. From its earliest inception, through the present, jihad has been central to the thought and writings of prominent Muslim theologians and jurists. The precepts and regulations elucidated in the 7th through 9th centuries are immutable in the Muslim theological-juridical system, and they have remained essentially unchallenged by the majority of contemporary Muslims. The jihad is intrinsic to the sacred Muslim texts, including the divine Qur'anic revelation itself, whereas the Crusades were circumscribed historical events subjected to (ongoing and meaningful) criticism by Christians themselves. Unlike the espousal of jihad in the Qur'an, the constituent texts oof Christianity, the Old and New Testaments of the Bible, do not contain a form fruste institutionalization of the Crusades. The Bible sanctions the Israelites conquest of Canaan, a limited domain, it does not sanction a permanent war to submit all the nations of humanity to a uniform code of religious law. Similarly, the tactics of warfare are described in the Bible, unlike the Qur’an, in very circumscribed and specific contexts. Moreover, while the Bible clearly condemns certain inhumane practices of paganism, it never invoked an eternal war against all of the world’s pagan peoples. The Crusades as an historical phenomenon were a reaction to events resulting from over 450 years of previous jihad campaigns. At the close of the 11th century, particularly after the crushing Byzantine defeat by the Seljuk Turks at Manzikert in 1071, Christendom, including Europe, was under existential threat by a confluence of Muslim advances. To the West, the Almoravid Berber Muslim tribes drove into Spain and pushed northward, pillaging and massacring the Christian populations they encountered. In the East, following their victory at Manzikert, the Seljuks put Armenia to fire and sword, and within a decade they had conquered three-fourths of Asia Minor.