Why Did the Crusades Start?

The Crusades began in 1095, when Pope Urban II called for a great military expedition to the Holy Land at the Council of Clermont. The reasons behind the call were many, and they had been building for decades. The standard modern account, by Jonathan Riley-Smith, is that the Crusade was essentially a devotional act — a way for the Latin Church to channel the violent energies of the lay nobility into a sacred cause that enhanced papal authority. The older “pluralist” view, by Carl Erdmann and others, was that the Crusade was the convergence of several distinct pressures (religious, economic, social, political) and that no single cause was sufficient. The short answer is that the Crusades began because a unique combination of religious enthusiasm, papal ambition, Byzantine appeal, and Western social pressure converged in the late 11th century — and that the modern debate is really about which of these was the necessary cause and which were the sufficient ones.

For a more detailed treatment, see the causes of the Crusades. For the broader story, see the main article on the Crusades.

The Religious Factor

The dominant motivation, at least in the eyes of contemporaries, was religious. Christian pilgrims had visited the Holy Land for centuries, but by the 1070s the route was disrupted by the Seljuk Turks. The papacy, led by the reformist Pope Urban II, saw an opportunity to channel the martial energies of Western knights into a sacred cause. The promise of remission of sins made participation irresistible to many.

The Byzantine Request

In March 1095, the Byzantine Emperor Alexios I Komnenos sent an appeal to Urban II, asking for Western military help against the Seljuk Turks, who had overrun most of Anatolia after the Battle of Manzikert in 1071. The Byzantine request gave the pope a practical justification for the expedition and shaped its eastern focus.

The Papal Agenda

Urban II was the leading figure of the Gregorian reform movement. He saw the expedition as a way to extend papal influence over the violent lay nobility of Western Europe, to reassert the Church’s moral authority, and to assert leadership of the Christian world against the Greek East. The Crusades would serve the papacy in all these ways, but the papacy would also lose control of the movement, especially after the Sack of Constantinople in 1204.

By 1095, Western Europe was overpopulated with landless knights. Younger sons of noble families had little to inherit, and the practice of primogeniture left them with no place in the feudal order. The Crusades offered them a chance to win land, wealth, and honor in distant lands. The response to Urban’s call showed how powerful this pressure had become.

What Happened Next

Within months of Urban’s speech, tens of thousands of men, women, and children had taken the cross. The People’s Crusade set out first, ahead of the main army, and was largely destroyed. The main army of the First Crusade followed and, against all odds, captured Jerusalem in 1099. The result was two centuries of further expeditions, examined in the Timeline of the Crusades.

A Historical Debate

Historians continue to debate the relative importance of the various causes. Older scholarship, sometimes called “pluralist” because it emphasized many causes, gave roughly equal weight to religion, economics, and politics. More recent scholarship, especially the work of Jonathan Riley-Smith, has emphasized religious motivation as primary. Riley-Smith argued that the Crusades were essentially devotional acts, motivated by the desire to fulfill the vow of pilgrimage and to win the spiritual benefits offered by the pope.

Other historians, like Thomas Madden, have continued to emphasize the political and economic dimensions, while still acknowledging the genuine religious fervor. The truth is probably a mixture: religion provided the language, the framework, and the ultimate justification, while politics, economics, and social pressure provided the practical reasons why people actually marched.

The Resulting World

Whatever the precise balance of causes, the result was a transformation of the medieval world. The Crusades created new institutions, including the military religious orders like the Knights Templar and the Knights Hospitaller. They reshaped the geography of Christendom, founding the Kingdom of Jerusalem and the other Crusader States. They opened a channel of exchange between Latin and Greek Christendom, which, ironically, would be cut short by the Sack of Constantinople in 1204. And they left a long legacy in the cultural and political memory of both Christian and Muslim worlds.

A Note on Terminology

It is important to remember that contemporaries did not always use the word “crusade” in the modern sense. The Latin terms iter (journey) and passagium (passage, expedition) were more common in the 12th century. The term crux, or cross, referred to the cloth symbol worn on the garments of those who had taken the vow. The modern use of “crusade” as a generic name for the whole movement is a later development, popularized by historians of the 17th and 18th centuries. Theologians have, in turn, sometimes argued about whether the term is even appropriate. What is clear is that the movement included a wide variety of expeditions, some of which had very little in common with the First Crusade that launched it all.