The Crusades Were Religious Wars. But Were They Fought to Spread Christianity?

In November 1095, Pope Urban II addressed a gathering of clergy and nobles at Clermont, in central France. The council had come together to deal with matters concerning the Church, but Urban also wanted to draw attention to a crisis farther east. The Byzantine Empire was struggling against Turkish powers, and he called upon western Christians to take up arms.

The response helped set in motion an extraordinary expedition. Thousands prepared to leave their homes and cross Europe into lands most had never seen. Wealthy nobles could afford to bring substantial military retinues, while others had to find whatever means they could to make the journey. It was expensive, dangerous, and likely to take years. Many of those who departed would never return.

On July 15, 1099, crusading armies captured Jerusalem. The conquest was followed by widespread killing, described even by Christian chroniclers in language that conveyed the brutality of what had occurred. Muslim and Jewish inhabitants suffered, and the crusaders established Christian rule over a city that had been governed by Muslims for centuries.

Looking at the outcome, it is understandable why people might describe the Crusades as wars to spread Christianity by force. Christian armies had invaded Muslim-held territory, seized one of the world’s most important religious cities, and placed it under Christian authority. But we still need to ask what they were trying to accomplish. Did the Crusaders set out to convert the people they conquered, or did they have another objective in mind?

An Empire in Trouble

Throughout much of the eleventh century, the Byzantine Empire struggled to maintain control of Anatolia. In 1071, its army suffered a major defeat at the hands of the Seljuk Turks at Manzikert. The battle is often presented as the moment Byzantium lost Anatolia, but the decline was not that immediate or straightforward. Civil wars, rival claimants to the throne, and continued Turkish advances gradually weakened imperial control over the following decades.

Alexios I Komnenos inherited these problems when he became emperor in 1081. He spent much of his early reign trying to stabilize the empire, and by 1095 he was seeking military help from the West. Byzantine representatives appeared that year at the Council of Piacenza, attended by Urban II.

We do not know precisely what Alexios asked for. The surviving accounts are limited, and historians continue to debate how much influence his request had upon the expedition that eventually emerged. What seems clear is that he needed help recovering territory from Turkish powers. Nothing in the surviving accounts presents his request as a campaign to convert Muslims.

What Urban encouraged later that year became far more than an army sent to assist the emperor. Its participants undertook a religious journey, received spiritual privileges, and ultimately made Jerusalem their principal destination. That was no small development, since Jerusalem had not been under Byzantine control for more than four centuries.

Muslim armies had conquered the city in the seventh century, after which it passed among different Muslim rulers. Christians continued to regard it as sacred, particularly because of its association with the crucifixion and resurrection of Jesus. Whatever the Byzantine emperor needed, Jerusalem carried a religious significance for western Christians that went well beyond Constantinople’s immediate military concerns.

To understand how these different concerns became part of the same expedition, we need to look more closely at Urban’s appeal. That raises a problem of its own: we do not possess a verbatim record of what he said at Clermont.

What Did Urban II Actually Ask Christians to Do?

Several medieval writers preserved versions of Urban’s speech, including Fulcher of Chartres, Robert the Monk, and Guibert of Nogent. None recorded it as it was delivered, and their accounts were written after the council. Each presents the appeal somewhat differently. They are valuable sources, but they also tell us how the First Crusade was understood and remembered after its success.

Fortunately, we have something closer in time to the event. In a letter to Christians in Flanders, generally dated to December 1095, Urban described the devastation of Eastern churches and the condition of Jerusalem, which he portrayed as suffering under intolerable foreign domination. He explained that he had traveled through France urging Christians to liberate the churches of the East, and he connected participation in the expedition with the remission of sins.

The letter is brief, so it would be a mistake to treat it as a complete account of everything Urban believed or intended. Even so, it gives us a reasonably direct statement of what he was asking Christians to do. He spoke of liberating churches and recovering sacred territory, with spiritual benefits promised to those who undertook the journey. He did not identify converting the Muslim population as an objective.

That does not prove that nobody involved in the movement hoped for conversions. It does, however, challenge a common assumption. Taking possession of a place because it is sacred to your religion is not necessarily the same thing as setting out to make its inhabitants adopt that religion.

Nor should we assume that everyone who answered Urban’s call had the same motives. The participants came from different regions and social circumstances. Some became military leaders, while others barely managed to survive the journey. Their reasons for going were not always identical.

The financial cost alone should give us some pause before treating the expedition as an easy opportunity for plunder. Historian Jonathan Riley-Smith’s work on crusading families shows how participants sold, mortgaged, or otherwise committed property to finance their departure. For many, going on crusade meant placing their wealth and security at considerable risk.

That does not mean wealth and ambition were absent. Bohemond of Taranto, for example, emerged from the expedition as ruler of Antioch, provoking serious tensions with the Byzantine emperor. Some participants undoubtedly hoped to gain territory or riches, and some did. But the ambitions of particular leaders do not explain everyone who joined. Pilgrimage, penitence, and the promise of spiritual reward were powerful motivations in their own right.

Jerusalem stood at the center of those hopes. For Christians who understood it as the place of Christ’s crucifixion and resurrection, reaching the city could be the fulfillment of a profoundly religious undertaking. They wanted it under Christian control. How they achieved that goal, however, would have terrible consequences for the people already living there.

Jerusalem and the Muslims Who Remained

By the summer of 1099, the crusading armies had reached Jerusalem. The city was controlled by Egypt’s Fatimid dynasty, which had taken it back from Turkish forces the previous year. After several weeks of siege, the crusaders breached its defenses on July 15.

The killing that followed remains one of the most notorious episodes of the First Crusade. Christian accounts describe extensive slaughter, sometimes using extravagant imagery to express the scale of the victory and its violence. Muslim writers likewise remembered the conquest as a catastrophe. We cannot establish a reliable total for those killed, and individual descriptions are open to debate. The massacre itself, however, is not seriously disputed.

Jerusalem had been brought under Christian rule, but its inhabitants had not been brought into Christianity. Many were killed, displaced, or expelled. The city’s religious character was transformed primarily through conquest and the establishment of a new political order, not through a systematic effort to baptize its population.

What happened beyond the city is equally important to the question. The new Latin Kingdom of Jerusalem governed territories where many Muslims continued to live, particularly in rural communities. They farmed land, paid dues, and remained part of the economy under Frankish rulers. If the purpose of conquest had been to turn every subject into a Christian, we would expect that objective to appear much more consistently in the way these communities were governed.

Admittedly, their experiences are not always easy to reconstruct. Much of the surviving Latin documentation records the concerns of landlords, religious institutions, and political officials rather than the lives of ordinary Muslim villagers. Benjamin Z. Kedar helped draw scholarly attention to these populations, while Ronnie Ellenblum’s research on rural settlement revealed patterns that were largely absent from older histories.

Ann E. Zimo’s more recent study adds Arabic sources and archaeological evidence to the picture. She challenges the idea that the kingdom consisted of two neatly separated societies, one Christian and the other Muslim. Their interactions were more extensive and varied than that model suggests. Muslims took part in the kingdom’s economic, legal, and social life, even if their presence is sometimes difficult to see in Latin accounts.

We should not mistake coexistence for equality. Latin Christians held the political power, and that power had been established through war. Still, Muslim communities could continue practicing Islam under Christian government. Maintaining Frankish rule did not depend upon converting every person subject to it.

The military orders make this especially interesting. The Templars and Hospitallers were religious institutions whose members took vows and fought against Muslim powers. Yet Alan Forey’s study found little indication that they made the conversion of their Muslim dependents a priority. In some circumstances, the orders were even reluctant to allow Muslim vassals and slaves to convert voluntarily. Established arrangements involving labor, service, and revenue could be disrupted by a change in religious status.

This was hardly a principled defense of religious freedom. Economic interests could take precedence over conversion, and we should not assume that every member of the orders thought alike. Nevertheless, it is difficult to square this evidence with the idea that their central purpose was to make all Muslims Christian.

A more personal glimpse of life under Frankish rule comes from Usama ibn Munqidh, a twelfth-century Muslim nobleman who knew the Franks well. In his writings, Usama described a visit to Jerusalem, where the Templars had established their headquarters in the al-Aqsa complex. Although they occupied the principal mosque, they allowed him to pray in a smaller building nearby.

During one visit, a newly arrived Frank interrupted Usama’s prayers and tried to turn him toward the Christian direction of prayer. The Templars removed the man, only to intervene again when he returned and repeated the behavior. Usama used the story to distinguish between newcomers and Franks who had grown accustomed to living alongside Muslims.

Of course, Usama was a well-connected visitor, not an ordinary peasant living under Frankish authority. His experience cannot tell us how all Muslims were treated, much less prove that the kingdom was tolerant. But it does give us a scene worth considering: Christian warriors occupied a Muslim holy site and nevertheless intervened so a Muslim visitor could continue his prayers. There was no demand that he convert.

None of this means forced conversion was absent from the First Crusade’s wider history. To find some of its clearest examples, we have to return to Europe and look at what happened even before the main armies reached the East.

The Violence of 1096

In the spring and summer of 1096, Jewish communities along the Rhine were subjected to devastating attacks by groups associated with the crusading movement. Speyer, Worms, and Mainz were among the cities affected. These were communities that had lived in western Europe for generations. They bore no responsibility for the Byzantine Empire’s military troubles, and some Christian authorities tried to protect them. Yet they became targets of violence within the movement Urban’s appeal had helped set in motion.

The massacres are often summarized as a simple choice imposed upon Jews: accept baptism or die. Forced baptism certainly belongs to the history of these attacks, but the sources do not always describe events unfolding in that order. David Malkiel’s examination of Jewish and Christian narratives suggests that some assaults began with killing, while opportunities to convert sometimes arose later, when Christians who personally knew the victims intervened on their behalf.

We also need to be careful about how much detail these narratives can establish. They were written with religious purposes in mind, and some were revised long after the events. Their authors were not necessarily trying to reconstruct the exact sequence of every assault. The evidence does not point to one consistent procedure followed everywhere. Murder, plunder, religious coercion, and forced baptism appeared in different combinations.

That qualification does nothing to diminish the atrocities. In some cases, the attackers appear to have been more interested in killing Jews than in securing their conversion. If so, we are dealing with something even harder to fit into the familiar description of crusading as an effort to spread Christianity. The violence was religious, but it did not always operate as a campaign to gain converts.

The Rhineland massacres were part of the history of the First Crusade, and they should not be treated as a footnote to its march on Jerusalem. At the same time, they cannot simply be taken as a statement of what the expedition to Jerusalem had been organized to accomplish. A movement proclaimed for one purpose could unleash attacks against people who had nothing to do with the conflict that prompted it.

Conversion did, however, become a more explicit objective in some of the crusading campaigns that followed.

When Crusading Moved Beyond Jerusalem

In 1147, a crusade was directed against pagan Wendish populations along the southern Baltic coast. It formed part of the broader movement of the Second Crusade, but it was not an attempt to recover Jerusalem or other sacred sites in the Holy Land. The Wends lived near expanding Christian powers, and bringing them into Christianity was one of the campaign’s concerns. So were territory, tribute, and the interests of neighboring rulers.

During the thirteenth century, similar campaigns unfolded in Livonia and elsewhere around the Baltic. Bishops, armies, and military orders worked to bring pagan communities under Christian authority. Baptism could accompany submission to new rulers, the establishment of churches, and the reorganization of political life. Religious and territorial expansion were often difficult to separate.

A papal letter from November 1226 is particularly useful here. Writing to the Brothers of the Sword in Livonia, Pope Honorius III addressed the question of crusaders who wanted to remain in the region after their original service had ended. He allowed the order to retain these volunteers and described them as men who had come to defend or expand the Catholic faith.

That wording tells us something about what crusading could mean by the thirteenth century. Urban’s original appeal had focused on aid to Eastern Christians and the recovery of sacred places. In Livonia, where there was no equivalent of Jerusalem to reclaim, the expansion of Christianity itself could serve as a justification for military action.

We should not read more into the letter than it says. Honorius was discussing military service, not setting out instructions for forcing people to be baptized. Even so, the expansion of the faith was now openly recognized as a purpose of crusading in the Baltic.

Marek Tamm’s research traces how supporters of the Livonian Crusade developed arguments for a form of warfare that did not fit the earlier model of recovering Christian holy places. Defending newly established Christian communities remained important, but extending the faith into neighboring pagan territory could also justify a crusade. The results varied. Some communities accepted baptism through negotiation, others submitted under military pressure, and older religious practices often continued beneath the new Christian institutions. Conquest did not instantly produce a thoroughly Christian society.

Meanwhile, crusading was being used against enemies within Christian Europe itself. In 1209, the Albigensian Crusade began against the Cathar movement and its supporters in southern France. Its targets lived in a predominantly Christian society, but the Catholic Church regarded their beliefs as heretical. The campaign brought sieges, massacres, confiscations, and opportunities for northern French nobles to extend their power. Its religious purpose was to suppress heresy and enforce conformity, not to introduce Christianity to people who had never encountered it.

By this point, crusading could be directed against Muslims, pagans, heretics, and even political opponents of the papacy. Similar spiritual privileges accompanied campaigns with quite different aims. It makes little sense to assign one motive to every crusade merely because they belonged to the same religious institution.

Nor were military campaigns the only way medieval Christians approached the question of conversion. During the Fifth Crusade, in 1219, Francis of Assisi crossed into Muslim-controlled territory in Egypt and met Sultan al-Kamil. The surviving accounts disagree on details, and later retellings have sometimes reshaped the encounter to suit their own concerns. Francis hoped to communicate his Christian faith to the sultan, while crusading armies pursued their military campaign in Egypt. His visit is a useful reminder that Christians could share a desire for the advancement of their religion while disagreeing over how that should happen.

What Were the Crusades Really About?

If we begin with Jerusalem in 1099 and then jump to the Baltic campaigns of the thirteenth century, we can easily miss how much crusading changed in between. The First Crusade grew out of an appeal to aid Eastern Christians and recover places considered sacred. Its armies committed terrible violence and established Christian political rule, but the expedition was not principally organized to convert Muslims. Some later crusades, particularly in northern Europe, made the spread of Christianity a more explicit goal. Campaigns against heretics had another aim again: enforcing religious conformity among people already living in a Christian society.

This does not make the First Crusade any less religious, and it certainly does not excuse what its participants did. The religious nature of the movement is not in dispute. What needs examining is the purpose for which religious warfare was undertaken in each setting.

It is also why neither of the familiar explanations works very well on its own. The Crusades cannot all be described as wars to convert non-Christians by force, but neither were they all defensive campaigns to protect Christian lands. They involved sacred places, political authority, territorial ambitions, penitence, and, at times, the deliberate expansion of Christianity. The weight given to those purposes changed from campaign to campaign, and individual participants could have motives of their own.

The Crusades were religious wars. That much is clear. But before saying that they were fought to spread Christianity, we need to ask which crusade we are talking about, whom it targeted, and what those who organized it actually intended to achieve.