The historiography of the Crusades has been a controversial topic since at least the Protestant Reformation. The term croisades was first used to refer to the entire period from the First Crusade until the fall of the Kingdom of Jerusalem in French historiography of the 17th century. The 18th-century Enlightenment ideology as represented by Edward Gibbon and Voltaire held up the Crusades as an example of medieval barbarism, while 19th-century Romantic nationalism tended to paint them in a heroic light, surrounding the Crusades with an aura of romance and grandeur, of chivalry and courage. In the second half of the 20th century, western historiography again tended to be more critical of the Crusades, following Steven Runciman (1951-4) Popular opinion, influenced by general trends of decolonisation and critical theory tended to portray the crusades with a sense of "western guilt". In early 21st literature, a "pluralist" view has become common which treats the "crusades" as a wider phenomenon of "all those medieval military endeavors that were penitential in nature (like pilgrimages), were authorized by bishops or the Pope, and whose participants typically engaged in the rite of taking the cross and the crusader’s vow".
In Eastern Orthodoxy, the Crusades had always been viewed in light of the disastrous attack on Constantinople in the Fourth Crusade, while in the Islamic world, the Crusades were mostly ignored prior to the growth of Arab nationalism in the 20th century.
The relevant medieval historiography of the period is edited in Recueil des historiens des croisades (RHC, 1841–1906). The RHC is divided into five series: 1. Lois ("Laws", i.e. the Assizes of Jerusalem), 2. Historiens occidentaux ("Western historians", i.e. texts in Latin and Old French), 3. Historiens orientaux ("Eastern historians", i.e. Arabic texts), 4.. Historiens grecs ("Greek historians") and 5. Historiens arméniens ("Armenian historians")
Important western histories include the Gesta Francorum, William of Tyre's Historia Ierosolimitana, Peter Tudebode , Raymond of Aguilers, Fulcher of Chartes, Gesta Tancredi, Robert the Monk, Baldric of Dol, Albert of Aachen Ekkehard of Aura, Caffaro di Rustico da Caschifellone, Walter the Chancellor, Benedetto Accolti the Elder. Greek Orthodox historians: Michael Psellos, Anna Komnene, John Kinnamos, Niketas Choniates, Nicephorus Gregoras, George Acropolites. The Eastern Orthodox view of the Crusades is dominated by the sack of Constantinople and the establishment of the Frankokratia in the Fourth Crusade in 1204. While the First Crusade was declared upon the request of the Byzantine Emperor, and concluded in triumphal success, the Crusades as a whole resulted in the terminal decline of the Byzantine Empire. Although the Byzantine Emperors were restored in 1260, the empire could never fully recover until eventually, weakened by civil wars, it fell to the Ottomans in 1453.
Armenian historians: Matthew of Edessa (d. 1144), Nerses Shnorhali (d. 1173), Michael the Syrian (d. 1199), Kirakos Gandzaketsi (d. 1271), Nerses of Lambron (d. 1198), Sempad the Constable (d. 1276), Hayton of Corycus (fl. 1307).
Relevant eastern (Muslim) historiographies include works by Ali ibn al-Athir (d. 1233), Baha ad-Din ibn Shaddad (d. 1234), Abd al-Latif (d. 1231), Ibn Jubayr (d. 1217), Ibn Khallikan (d. 1282), Abu al-Feda (d. 1331). Contemporary Muslim historiographers such as Ali ibn al-Athir refer to the Crusades as the "Frankish Wars" ( حروب الفرنجة). The term used in modern Arabic, حملات صليبية ḥamalāt ṣalībiyya, lit. "campaigns of the cross" is a loan translation of the term crusade as used in Western historiography. Later Muslim historiography did not focus on the Crusades as a single or coherent event. One main reason for this is that the Crusades in retrospect figure as more of a marginal issue compared to the final collapse of the Caliphate under the Mongol invasions and the eventual replacement of Arab rule by the Turkish Ottoman Empire, which suppressed Arab nationalism for the following seven centuries. The end of the "Islamic Golden Age" is thus only partially due to the Crusades, and more notably to the Turkic and Mongol expansions. According to modern historians of Islamic history such as Murphy (1976) and Mansfield (2003), the collapse of the Caliphate led to the development of "intellectual barriers" and "isolationist policies" in the Muslim world.
Notable contemporary accounts by Jewish authors include the Solomon bar Simson Chronicle (c. 1140), the chronicle of Eliezer bar Nathan (d. 1170), the Mainz Anonymous, and the works of Ephraim of Bonn (d. 1200).
Influential historiographical works on the Crusades include:Voltaire, Histoire des Croisades (1750, 1751)
Edward Gibbon (1776–1789), edited as The Crusades (1870);
Charles Mills, History of the Crusades for the Recovery and Possession of the Holy Land (1820);
Joseph François Michaud, Histoire des Croisades (1811–1840)
René Grousset, L'Histoire des croisades et du royaume franc de Jérusalem est un livre d'histoire, 3 vols. (1934–1936)
Steven Runciman, A History of the Crusades (1951-4);
Christopher Tyerman, God's War: A New History of the Crusades (2006).
The popular prevailing view in the nineteenth and early twentieth century originated in the writings of the Scottish novelist Sir Walter Scott and the French historian Joseph-Francois Michaud. Scott published four crusade based novels between 1819 and 1831. Influenced by the Enlightenment and the philosopher-historian William Robertson Scott's view was the crusades were the incursions of glamorous but uneducated western Europeans into a superior civilization. Michaud published his influential Histoire des croisades between 1812 and 1822 depicting the crusades as glorious instruments of nationalism and proto-imperialism. These incompatible views agreed only on a crusade was defined by its opposition to Islam, but began to merge in the 1920s as crusading began to be interpreted in social and economic terms by Liberal economic historians within an imperialist context assuming that crusading was an early example of colonialism. So Scott's Enlightenment inferior culture attacking a more sophisticated culture mixed with Michaud's Romantic proto-colonialist conviction. By the 1950s this established a neo-imperialistic and materialistic orthodoxy that remains the popular perceptions.
Steven Runciman's three volume History of the Crusades (1951–54) is seen by some to mark a turn from the idealization of the Crusades as heroic enterprise in the 19th century to their denunciation as a barbarian invasion primarily of the Byzantine Empire. Peters (2011) says that Runciman's work "instantly became the most widely known and respected single-author survey of the subject in English." Riddle (2008) says that for his day Runciman was the “greatest historian of the Crusades.” He reports that, “Prior to Runciman, in the early part of the [20th] century, historians related the Crusades as an idealistic attempt of Christendom to push Islam back.” Runciman regarded the Crusades “as a barbarian invasion of a superior civilization, not that of the Muslims but of the Byzantines.” Madden (2005) stresses the impact of Runciman’s style and viewpoint:
It is no exaggeration to say that Runciman single-handedly crafted the current popular concept of the crusades. The reasons for this are twofold. First, he was a learned man with a solid grasp of the chronicle sources. Second, and perhaps more important, he wrote beautifully. The picture of the crusades that Runciman painted owed much to current scholarship yet much more to Sir Walter Scott. Throughout his history Runciman portrayed the crusaders as simpletons or barbarians seeking salvation through the destruction of the sophisticated cultures of the east. In his famous "summing-up" of the crusades he concluded that "the Holy War in itself was nothing more than a long act of intolerance in the name of God, which is a sin against Holy Ghost.”
An attempt at an updated account of the period was presented by Christopher Tyerman with his God's War: A New History of the Crusades (2006).
Secular critics of the crusades has paralleled the Crusades with the Islamic concept of jihad as comparable approaches to a religious justification of war. The opposing position emphasizes the offensive nature of Islamic jihad as opposed to the intrinsically defensive nature of the Crusades as a project to re-conquer territory lost to the Islamic expansion. This debate has notably taken place in the context of contemporary Jihadism and the US 2003 invasion of Iraq.
James Illston says "the field of medieval gender studies is a growing one, and nowhere is this expansion more evident than the recent increase in studies which address the roles of medieval women in times of war....this change in research has been invaluable." He provides a 20-page bibliography of dozens of recent scholarly books and articles, most of them connected to the crusades.
Apart from the technical scholarship, a plethora of popular treatments have appeared in the early 21st century. Thomas Madden has discussed modern misconceptions about the Crusades that appear in nonscholarly writings.
In Jewish historiography, the Crusades are mostly seen in the context of their being accompanied by the first displays of antisemitism in medieval Europe. The social position of the Jews in western Europe was distinctly worsened, and legal restrictions increased during and after the Crusades.
The crusades and their leaders were romanticized in popular literature of the late medieval period; the Chanson d'Antioche was a chanson de geste dealing with the First Crusade, and the Song of Roland, dealing with the era of the similarly romanticized Charlemagne, was directly influenced by the experience of the crusades, going so far as to replace Charlemagne's historic Basque opponents with Muslims. A popular theme for troubadours was the knight winning the love of his lady by going on crusade in the east.
In the 14th century, Godfrey of Bouillon was united with the Trojan War and the adventures of Alexander the Great against a backdrop for military and courtly heroics of the Nine Worthies who stood as popular secular culture heroes into the 16th century, when more critical literary tastes ran instead to Torquato Tasso and Rinaldo and Armida, Roger and Angelica. Later, the rise of a more authentic sense of history among literate people brought the Crusades into a new focus for the Romantic generation in the romances of Sir Walter Scott in the early 19th century. Crusading imagery could be found even in the Crimean War, in which the United Kingdom and France were allied with the Muslim Ottoman Empire, and in World War I, especially Allenby's capture of Jerusalem in 1917.
In Spain, the popular reputation of the Crusades is outshone by the particularly Spanish history of the Reconquista. El Cid is the central figure. In a broader sense, crusade was used, in a rhetorical and metaphorical sense, to identify as righteous any war that was given a religious or moral justification.
Linder (2001) examines 15th-century Catholic Church liturgy designed to generate support for the war effort against the Turks and to legitimize its aims. Two types of Missae Contra Turcos were used: masses converted to this function through the addition of appropriate three core prayers and complete dedicated masses. The most popular example of the first type was the triple prayer set originally established by Clement V as a Holy Land crusade liturgy and subsequently mobilized against the Turks. The second type is represented by nine different mass formularies that were introduced after the fall of Constantinople in 1453. Most surviving liturgies are of German or French provenance, indicating extensive use not only among the front-line populations but also in areas far removed from any threat. The liturgy displays its intense crisis rhetoric. Its predominant stance of vulnerability and defensiveness entailed aggressive mobilization and the conceptualization of the Turk as the actual, specific manifestation of the generic infidel, the competing religious Other; and the remarkable continuity - in form and in content - that linked this liturgy with its parent liturgies (mainly those of the campaigns against the pagans and the Holy Land Crusades) further accentuated these traits. The communicative function and value of this liturgy is highlighted by the concentration of the direct, unmediated communicative elements in that part of the mass that was the most accessible to the laity.
In the 19th century, romantic writers like novelist Sir Walter Scott created heroic images of the crusaders. The romantics and conservative adherents of the European ancien régimes appropriated crusading imagery for their own 19th-century political goals, downplaying religion to fit within a modern, secular context and presenting crusades as a counterpoint to liberal ideas of nationalism.
The Salle des Croisades in the north wing of the Palace of Versailles opened in 1843, commissioned by king Louis-Philippe, at a time when France was seized with enthusiasm with its historical past, and especially the period of the Crusades. The rooms are filled with over 120 paintings related to the Crusades.
Knobler (2006) examines the use of the crusades as a national symbol from the 19th century to the 1910s in France, Spain, the Ottoman Empire, Ethiopia, Britain, Russia, and Bulgaria. The Enlightenment and its secular ideological successors held the crusades as an example of medieval barbarity. Enlightenment thinkers like historian-philosophers Voltaire and David Hume denounced the crusades, as did the historian of Byzantium Edward Gibbon, who wrote:
"The principle of the crusades was a savage fanaticism; and the most important effects were analogous to the cause…. The belief of the Catholics was corrupted by new legends…. The active spirit of the Latins preyed on the vitals of their reason and religion…. The lives and labours of millions, which were buried in the East, would have been more profitably employed in the improvement of their native country."
Knobler (2006) explores three primary themes: memory of the crusades as it relates to debates over the generation and use of national symbols; the crusader as a romantic hero; and the Muslim recollection of the crusades as a shameful blot on the past of Christian nations. The crusades appealed to many Europeans because they reflected a morally unambiguous time, sparked romanticized images of warfare in a time of imperialist expansion, and provided heroic templates for modern "crusading" imperialist heroes.
There was little interest in the crusades in Islamic culture prior to the 20th century. Phillips (2005) summarizes the general indifference by stating that "most Muslims" see the Crusades as "just another invasion among many in their history". The veneration of Saladin as chivalrous opponent of the Crusaders likewise finds no reflection in Islamic tradition before the visit of German Emperor Wilhelm II to Saladin's tomb in 1898. The visit, coupled with anti-imperialist sentiments, led nationalist Arabs to reinvent the image of Saladin and portray him as a hero of the struggle against the West. The image of Saladin they used was the romantic one created by Walter Scott and other Europeans in the West at the time. It replaced Saladin's reputation as a figure who had been largely forgotten in the Muslim world, eclipsed by more successful figures such as Baybars of Egypt. Modern Arab states have sought to commemorate Saladin through various measures, often based on the image created of him in the 19th-century west.
Renewed interest in the period is comparatively recent, arising in the context of modern Jihadist propaganda calling for war against the Western "crusaders". Notably, a fatwa signed by Osama bin Laden and Ayman al-Zawahiri in 1998 called for jihad against "the crusader-Zionist alliance" (referring to the United States and Israel). By 2008, The Oxford Encyclopedia of the Islamic World claimed that "many Muslims consider the Crusades to be a symbol of Western hostility toward Islam". The term ṣalībiyyūn "crusader", a 19th-century loan translation from Western historiography, is now in common use as a pejorative; Salafi preacher Wagdy Ghoneim has used it interchangeably with naṣārā and masīḥiyyīn as a term for Christians in general.