What are the Crusades?

by Luke Wayne

The Crusades are the wars that were fought between Roman Catholic Europe and the Muslim empires, as well as with other perceived enemies of European security or Roman Catholic orthodoxy, from the 11th to at least the 15th century. Before addressing the particular historical setting or motivations for specific crusades, like those against the Muslim nations, the fundamental question we have to ask is: What makes a war a crusade? What separates a crusade from other wars, even from other religiously motivated wars?

What is a Crusade?

The concept of a "crusade" is rooted deeply in the theology of medieval Roman Catholicism. It flows from the belief that one who performed acts of penance (works paired with confession done to remove punishment of sin in purgatory) at the instruction of a priest under papal authority would receive the remission of their sins. In proclaiming the First Crusade, Pope Urban II (1042-1099 A.D.), said:

"If those who set out thither should lose their lives on the way by land, or in crossing the sea, or in fighting the pagans, their sins shall be remitted. This I grant to all who go, through the power vested in me by God."1

He called for this as an act of penance specifically for previous sinful violence, saying:

"Let those who have been accustomed to make private war against the faithful carry on to a successful issue a war against the infidels, which ought to have been begun ere now. Let these, who for a long time have been robbers now become soldiers of Christ. Let those who once fought against brothers and relatives now fight against the barbarians."2

For later Crusades, Pope Innocent III (1160-1216) extended the remission of sins to those who built ships or made other necessary contributions to the war effort so long as they did so as an act of penance.3 A 13th-century Catholic preacher named Humbert of Romans (1200?-1277) went so far as to say in defense of the Crusades:

"By this kind of death people make their way to heaven who perhaps never would by any other means."4

A Crusade, therefore, is not merely a religious war. It is a war in which one's service is an act of penance through which one receives the promise of the remission of sin. Historian Jonathan Riley-Smith defined it thus:

"To crusade meant to engage in a war which was both holy, because it was believed to be waged on God's behalf, and penitential, because those taking part considered themselves to be performing an act of penance. The war was authorized by the pope as the Vicar of Christ. Most crusaders were laymen and women who committed to join an expedition by each making a vow. They were rewarded with indulgences, guarantees that the penitential act in which they were engaged would rank in God's eyes as a fully satisfactory remission of the sins they had committed up to that date" 5

So the Crusades, which were fought not only against the Muslims but also the Mongols, the proto-protestant Hussites, the heretical Cathars, and a variety of other perceived threats to Roman Catholic orthodoxy or the security of Europe,6 were a unique outgrowth of the practical theology of medieval Roman Catholicism, and so were more than simply a war in the name of religion. For those who were fighting, they were a labor of penance in the desperate hope of forgiveness. They were individual acts of Catholic piety on behalf of the combatants and were rooted in a specific theology of Papal authority, the merit of penance, and remission of sins mediated to the penitent through church authorities. In short, the whole idea of crusades is an outgrowth of the very theological errors that sparked the Protestant Reformation.

The Crusades against the Muslims

Understanding this ideological background, why did the popes call on men throughout Europe to take up arms against the Muslims? Why would they offer the remission of sins to those who would fight for this specific cause? To fully answer these questions, there are multiple historical factors and theological developments one must consider.

A World Divided

The world of the middle ages was a violent place. Among the upper classes of Europe, local lords and heads of wealthy families were given over to bloody feuds and vendettas. Among the peasantry and working classes, banditry and violent robbery were rampant.7 We can see this even in the quote given earlier where Pope Urban II declared the first crusade to be an act of penance for these very things.

The Muslim world fared no better. Having conquered much of the Middle East, North Africa, portions of India and South Asia, and even a large portion of southern Spain and parts of France,8 Islam had since become increasingly factionalized by both ideological and ethnic divisions. The result was a state of ongoing religious war and political intrigue within Islamic lands. Muslim conquest and expansion slowed significantly as the various peoples of the Islamic world turned on one another and battled for preeminence.9 Still, the Greek empire that held together what was left of the Greco-Roman East, Christian by profession yet divided from the Papacy of the Roman Catholic west, was weak from its own internal struggles and was losing its territory to the Muslim Turks.10 Thus both Europe and the Muslim world were already in violent struggles with themselves and with each other.

Reversing the Muslim Advance

It is in this context that Emperor Alexius I (1056-1118) of the Greek empire called upon Western Europe to come to their aid and help them beat back the advance of the Turks and reclaim their lost territory.11 This led to the announcement of the first Crusade being by Pope Urban II for the purpose of aiding the Greeks in the name of Christian brotherhood.12 The call was to "rush as quickly as you can to the defense of the Eastern Church."13

It should be noted that there was never a call to eradicate all Muslims, but rather to halt their advance and to reclaim territory that had been conquered by Islamic forces. Bernard of Clairvaux (1090-1153), a Catholic mystic who was one of the most influential preachers in medieval Catholicism, wrote regarding the crusades that "Pagans must not be slain if they can otherwise be prevented from oppressing the faithful." He said this in full support of the Crusades, explaining that "it is better that they be put to death than that the rod of the wicked should rest on the lot of the righteous."14 These Crusades were fought for the purpose of protecting the Greek and Roman Catholic nations from Islamic advance.

Protecting the Pilgrimage

There is still more to the story, however. Specifically reclaiming Jerusalem and the "Holy Land" also played a huge part in these endeavors from the very start.15 The centrality of this goal can scarcely be overstated. As late as the 1400s, Christopher Columbus actually took an oath that the proceeds of his venture would be used to recover the Holy Sepulchre in Jerusalem.16 The reason for this brings us back again to medieval Catholic theology and the merit of pilgrimage to holy sites and relics.

The Muslims occupying Jerusalem were not only occupying the city which held the most sacred sites of medieval Catholic pilgrimage; they were in some cases desecrating them. The "Holy Sepulchre" had been vandalized on the orders of the Muslim leader Caliph Hakim (985-1021), and the traditional site of "Christ's cave tomb" was leveled almost to the ground.17 Pilgrimages to such sites were considered meritorious acts of piety and penance, sometimes with official promises of remission of sins for visiting them, and often shrouded in stories of miracles, healings, and other divine favors on those who attended them.18 It was, therefore, of great interest to the Catholic Church and the masses of Europe to preserve these sites from desecration and to ensure continued freedom for pilgrims to journey to them. Jerusalem contained the most sacred and revered of these holy destinations.

This may seem to modern readers as if it must have been a secondary consideration. The reality is, however, that it centered prominently in almost all of the Crusade proclamations and is the only explanation behind why Jerusalem would hold such a central place in the aim of the Crusades when it was not at all central to the defense of Europe. This, too, finds the crusades inseparably linked to the false teachings and traditions which crept into the church over time and which the Protestant Reformation specifically set out to undo.


In summary, crusading flows out from an unbiblical theology unique to the medieval Roman Catholicism of Western Europe. The Crusades directed toward Muslim nations were not the breaking out of new and unprecedented violence in an otherwise peaceful world, but rather the refocusing of violence in a world of deep turmoil and hostile division on both sides. They involved political matters of national defense, and also deeply religious matters and eternal concerns. They were not carried out with genocidal intent, but for the protection of home, of neighbor, of sacred places, and in a misguided quest for a merited forgiveness in a dark world that knew full well that it was plagued with the sickness of sin.

  • 1. August Krey, The First Crusade, the Accounts of Eyewitnesses and Participants, (Princeton University Press, 1921), 38
  • 2. ibid, 39
  • 3. Phillip Schaff, History of the Christian Church, Volume 5 (Hendrickson Publishing, 1907) 217
  • 4. Jonathan Riley-Smith, The Crusades: A History, Third Edition (Bloomsbury, 2014) Kindle edition, Chap. 1
  • 5. ibid, Chap. 1
  • 6. ibid, Chap. 1, 7, 8
  • 7. Thomas Asbridge, The Crusades: The Authoritative History of the War for the Holy Land (Harper Collins, 2010) 7
  • 8. ibid, 19
  • 9. ibid, 20-22
  • 10. Riley-Smith, The Crusades: A History, Third Edition, Chap. 2
  • 11. Asbridge, The Crusades: The Authoritative History of the War for the Holy Land, 34
  • 12. ibid, 36
  • 13. Krey, The First Crusade, the Accounts of Eyewitnesses and Participants, 45
  • 14. Phillip Schaff, History of the Christian Church, Volume 5 (Hendrickson Publishing, 1907) 218
  • 15. Asbridge, The Crusades: The Authoritative History of the War for the Holy Land, 36
  • 16. Phillip Schaff, History of the Christian Church, Volume 5 (Hendrickson Publishing, 1907) 214-215
  • 17. Riley-Smith, The Crusades: A History, Third Edition, Chap. 2
  • 18. ibid, Chap. 2