The First Crusade and Just War Theory: An Evaluation of the Justification of the First Crusade

The First Crusade and Just War Theory: An Evaluation of the Justification of the First Crusade

By Sean Carnathan

Paper given at the National Conference on Undergraduate Research (2011)

Image from An introduction to American history, European beginnings (1919)

Image from An introduction to American history, European beginnings (1919)

Introduction:  From the confines of Jerusalem and the city of Constantinople a horrible tale has gone forth and very frequently has been brought to our ears, namely, a race from the kingdom of the Persians, an accursed race, a race utterly alienated from God…has invaded the lands of those Christians and has depopulated them by the sword, pillage and fire…. It has either entirely destroyed the churches of God or appropriated them for the rites of its own religion…. On whom therefore is the labor of avenging these wrongs and of recovering this territory incumbent, if not upon you? You, upon whom above other nations God has conferred remarkable glory in arms, great courage, bodily activity, and strength to humble the hairy scalp of those who resist you.

According to Robert the Monk, those powerful words were spoken by Pope Urban II in 1095, and were meant to incite a counterattack against the Muslims who had taken the Holy Land out of Christian hands. The question we must ask is, “Why would people listen to the Pope and undertake arms in the First Crusade – an unprecedented kind of war?” Was the First Crusade justified, according to Just War theory as known to medieval people? Such questions can be answered if one examines the sources of early Just War theory as applicable to the Crusades. When examining individual battles, or even wars, it is important to determine if those violent acts were considered justified by the standards of the time, so that any illusions of the past might be dispelled. In order to find out what constituted the just use of violence, one must look at the sources which medieval people would have used.

It is very easy to judge the past from a modern point of view – a kind of arm chair historian that evaluates history without understanding the standards of the time being studied. Luckily for us, by the time of this study, there are number of prominent figures that develop the idea of Just War theory, which provide us with a lens through which to evaluate wars during the time period. Furthermore, it may seem obvious, but the written record is the only method we can use to gauge what was considered to fall within the norms of society. Although this work focuses mainly on church figures, ancient philosophers such as Plato, Aristotle, and Cicero provide the basis for the Just War theory medieval people would have manipulated and edited. Early church fathers such as Ambrose of Milan, Augustine of Hippo, and Isidore of Seville provide an interpretation of the Bible and other Christian sources which medieval people would have regarded as dogma. Finally, sources from high and late medieval times, such as those written by Bernard of Clairvaux and Thomas Aquinas – provide a gauge to which we can determine popular thought regarding the morality of warfare around this time. Furthermore, because war in the Middle Ages can encompass private war and public war, we must differentiate between the two types and determine what makes a morally justifiable war as well as identify what type of war is being studied by sources available during the medieval period. Ultimately, the goal of this research is to determine the criteria for a justified war, as known to medieval people, and apply it to the reasons provided for the First Crusade.

Click here to read this paper from Robert Morris University


Sign up to get a Weekly Email from

* indicates required

medievalverse magazine