In This Article Expand or collapse the "in this article" section Christianity and Warfare in the Medieval West

  • Introduction
  • Primary Sources
  • General Overviews
  • Journals
  • Anthologies/Special Journal Issues
  • Biographies
  • Saints and Biblical Exemplars
  • Fighting Clerics
  • Just War
  • The Papacy
  • Canon Law
  • Ideology
  • Morale and Logistics
  • Military Orders
  • Peace-Making
  • Chivalry, Masculinity, and Religion

Military History Christianity and Warfare in the Medieval West
Craig M. Nakashian
  • LAST REVIEWED: 26 May 2023
  • LAST MODIFIED: 26 May 2023
  • DOI: 10.1093/obo/9780199791279-0233


The study of Christianity and warfare in the Middle Ages is usually focused on the following areas: the role that the church played in directing and prosecuting wars (such as holy wars and the Crusades), the development of theoretical frameworks to justify/condemn warfare in both general and specific contexts (such as just war theory and canonical legislation), the role that clergy played in regulating violence in medieval society (as in the peace and truce of God), and the role(s) that members of the clergy played in warfare. In one way or another, these topics have been debated since the days of the early church. The debate over the proper interaction between Christianity and warfare in the Middle Ages derived from a number of different factors, including the perceived pacifism of the founder of the religion, Jesus Christ. This led to an ideological argument over the appropriateness of violence by Christians. Early Christians debated whether Christians could shed blood, and once institutionalized they debated which Christians could shed blood, when, under what conditions, and what (if any) penance they needed to complete to return to communion with the church community. The writings of Saint Augustine on just war shaped the argument well into the Middle Ages. The long-standing efforts by the bishops of Rome to centralize clerical administration and ideology also fit into the discussion. As the bishops of Rome asserted their roles as the ecclesiastical heads of Christianity, they worked with and against secular rulers to establish church governance throughout Europe. This religious edifice was reinforced by the development and codification of canon law, which sought to regulate the behavior of clerics, including in warfare. Clerics also sought to regulate violence in society more broadly, especially to restrain the warfare of a fractious nobility. Holy wars, including those hearkening back to examples from the Old Testament, and Crusades further entwined Christianity and warfare. Christianity, and its church(es), was now at the forefront of directing, supporting, and endorsing warfare, often offering spiritual benefits for the participants. Crusades, members of the military orders, and ordinary knights now operated in a world where spiritual (and temporal) benefits could accrue to those fighting in licit causes endorsed clerical leaders. Despite the major divisions caused by the Reformation, something that Roman Catholic and Protestant Christians could agree on was that God was on their side in their wars against each other.

Primary Sources

There are countless examples of primary sources that shed light on the interplay between warfare and Christianity in the medieval West. Almost every medieval chronicler engaged with the topic, some at great length, so choosing among them can be difficult. Similarly, much of the imaginative literature of the time reflected these concerns over religion and warfare. Still, below are representative examples of the primary sources available on this topic; others are referred to in the secondary entries contained in the rest of this bibliography. The writings of Saint Augustine: Works, especially in his City of God and his Contra Faustum Manichaeum, helped to develop a philosophical underpinning of licit Christian warfare. Bishop Gregory of Tours’ History of the Franks gives a contemporary account of the (sometimes violent) conversion of the Franks to Christianity. Anna Comena’s Alexiad discusses her father Emperor Alexius Comenus I and his efforts to secure the Byzantine throne, while also commenting on her impressions of the Latin Christian crusaders. Shaw 1963 offers translations of two 13th-century French sources on crusading. Brault 1978 translates one of the most popular epic poems from the twelfth century, demonstrating notions of holy war and Crusade. Newth 1989 translates a lengthy chanson de geste focusing on the interaction of warfare and Christianity. Peters 1998 brings together a wide array of sources to illuminate the First Crusade. Brundage 2003 translates a narrative from the Crusades to the Baltic region. Pavlac 2008 gives a translation of the life of Archbishop Albero of Trier, a consummate German warrior-prelate. Allen and Amt 2010 compiles a series of texts from the early Middle Ages through the early modern period to demonstrate ideas of holy war and Crusade.

  • Allen, S. J., and Emilie Amt, eds. and trans. The Crusades: A Reader. Toronto: University of Toronto Press, 2010.

    A largely chronological arrangement of materials related to the origins of crusading, through the traditional Crusades, and including Crusades outside of the Holy Land. Taking a pluralist approach to Crusades, the collection features materials on Western Latin, Eastern Greek, and Arabic authors. Also features a culminating section examining how crusading shifted in the early modern period.

  • Anna Comena: The Alexiad.

    Mid-12th-century account of the reign of Emperor Alexius Comenus I of the Byzantine Empire, written by his daughter Anna. Includes materials of her father’s wars against non-Orthodox Christians and her impressions of Latin Christians during the early Crusades.

  • Brault, Gerald J., ed. and trans. Song of Roland: An Analytical Edition. 2 vols. University Park: Pennsylvania State University Press, 1978.

    The Song of Roland is among the best-known pieces of medieval epic poetry from the period of the early Crusades. It is based on a fictional invasion of Spain by Charlemagne and contains themes of holy war, meritorious Christian sacrifice, and crusading.

  • Brundage, James A., ed. and trans. The Chronicle of Henry of Livonia. New York: Columbia University Press, 2003.

    An early-13th-century chronicle account of the conquest and conversion of the Baltic region to Christianity from a priest accompanying the crusader forces.

  • Gregory of Tours. The History of the Franks. Translated by Lewis Thorpe. New York: Penguin, 1974.

    Seminal account of the rise of the Frankish kingdom and its transition into a Christian state embracing the Roman Christian church. Written by Gregory of Tours (d. 594), a Romano-Gallo author and bishop.

  • Newth, Michael A., trans. The Song of Aspremont. New York: Garland, 1989.

    A twelfth-century chanson de geste chronicling a fictional war between the forces of Charlemagne and those of the non-Christian king Agolant. Features themes of war, religion, and violence, as well as the chivalric exploits of Archbishop Turpin.

  • Pavlac, Brian A., ed. and trans. A Warrior Bishop of the Twelfth Century: The Deeds of Albero of Trier, by Balderich. Toronto: Pontifical Institute, 2008.

    A translation of the Deeds of Albero by Balderich (a 12th-century German chronicler). Themes include conflicts between secular and religious figures, as well as the proper role for clerics in warfare. Features commentary and notes by the translator.

  • Peters, Edward, ed. The First Crusade: The Chronicle of Fulcher of Chartres and other source materials. 2d ed. Philadelphia: University of Pennsylvania Press, 1998.

    A compilation of sources related to the First Crusade. Arranged thematically by events, rather than by author, it features writings by Latin, Greek, and Muslim authors.

  • Saint Augustine: Works.

    The writings of Saint Augustine are foundational to our understanding of just war and have major implications for the interaction of Christianity and war.

  • Shaw, M. R. B., ed. and trans. Joinville and Villehardouin: Chronicles of the Crusades. London: Penguin, 1963.

    Translations of two crucial sources for 13th-century crusading, geared toward an academic as well as a popular audience. While other translations exist (and are more suited to a scholarly audience), this joint volume offers an ease-of-access and introduction for students and those interested in the Crusades.

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