Jay Rubenstein is well known to both scholars and lay enthusiasts for his interest in medieval apocalyptic thought following his popular, if somewhat controversial, Armies of heaven: the First Crusade and the quest for apocalypse (New York 2011). In this new book Rubenstein challenges conventional wisdom and recent historiography that assert that the apocalypse and the crusades had nothing to do with one another. Inspired by reading Guibert of Nogent (d. 1125), Rubenstein found that the conquest of Jerusalem was initially viewed by many as a world-changing event with apocalyptic connotations – a momentous occasion in history that would usher in the end times: ‘The First Crusade changed perceptions of the past – but also of the future’ (p. xvii). Like Guibert, however, before long contemporaries became disillusioned and apocalyptic speculation again shifted to Europe. Rubenstein's purpose is to highlight this strand of thought that interpreted the First Crusade in apocalyptic terms and to show how and why it was abandoned.

The first part of the book covers five chapters and sets the stage. Nebuchadnezzar's dream refers to the account recorded in the Book of Daniel in which the Babylonian king had dreamed of a colossal statue made of various metals. Each metal represented a successive kingdom, with the last (Rome) brought down by a stone uncut by human hand (that is, Christ) that would grow into a mountain and fill the earth to eternity. This interpretation of St Jerome went unchallenged until 1103, when Bohemond of Taranto, then a prisoner in Anatolia, had an epiphany: the stone uncut by human hand was not Christ, but was Bohemond and his friends.

By conquering Jerusalem, asserted the charismatic Bohemond, crusaders had fulfilled the prophecies of Nebuchadnezzar's dream. Lambert of Saint Omer, in his Liber Floridus, refined Bohemond's message and offered new interpretations of old prophecies in light of the crusade's success. Believing that human institutions were still capable of advancing the work of salvation, Lambert realised a connection between the crusade and apocalypse in the ongoing conflict between Christians and Jews (or Muslims). Lambert's vision of history, argues Rubenstein, was

Indeed, the First Crusade was the ‘opening act of the End Times’ (p. 63).

Rubenstein moves in part ii towards an analysis of the consequences of this view of history, which were also the source of Guibert's disillusionment. The idealised version was let down by subsequent failures (for example, in 1101 and 1107) and the unholy conduct of many returning crusaders. Reports about King Baldwin i adopting Greek and Saracen customs were viewed as a betrayal of Christian and Latin values, while the disastrous Battle of the Field of Blood (1119) demonstrated that God was angry and that Franks should not mix with Saracens.

In part iii, consisting of chapters viii–x, Rubenstein examines the impact of the Second Crusade on the memory of the First Crusade. The disillusion experienced by Guibert became more widespread. Christian theologians and intellectuals began to revise their apocalyptic interpretation of the First Crusade, writing Jerusalem and the Holy Land out of apocalyptic narratives. This was due not only to the colossal failure of the Second Crusade, argues Rubenstein, but also to the way in which it was promoted by St Bernard of Clairvaux. His preaching tour included hundreds of ‘miracles’ performed as evidence of God's favour, which even as they led to enthusiasm for the crusade, were harder to understand in the wake of its failure.

The shift away from the East can be noted in the writing of the Cistercian Otto of Freising, uncle of Frederick Barbarossa, who wrote that the empire and imperial authority had returned to Europe in 800 with Charlemagne's coronation. The apocalypse had actually already begun when Pope Gregory vii excommunicated Emperor Henry iv, launching the war between empire and papacy. Gerhoh of Reichersberg, Hildegard of Bingen and Ralph the Black further eliminated the Last World Emperor from the apocalyptic narrative, discussing the First Crusade in moral or spiritual terms and rejecting the liberation of Jerusalem as an objective.

Enthusiasm for crusading, argues Rubenstein in part iv, might have ended altogether had it not been for the fall of Jerusalem to Saladin in 1187. This caused further rethinking of history, prophecy and the place within it of the crusades. The First Crusade was no longer emulated and Jerusalem was no longer the centre of salvation history. The exception to this trend was Joachim of Fiore, who shared with Bohemond of Antioch a belief that the Latin West was destined to bring down Nebuchadnezzar's statue, of which Islam was most representative.

Rubenstein's aim in this book is to demonstrate that apocalyptic concerns were as legitimate a motivation for Crusaders as was penance. ‘Embrace of the apocalyptic … indicated a wish to understand history and a belief that humanity still had an important role to play in God's plan for salvation’ (p. 214). Clergy and the military class were brought together in their fascination with the Last Days (viewed as heroic adventure and the climax of history) and the thought that they were at hand. Not dissimilarly, Rubenstein concludes by drawing attention to contemporary apocalyptic worldviews, particularly amongst Evangelical Christians as well as some Sunni and Shi'a Muslims. For many Christians, Muslims as well as Jews, Jerusalem remains the epicentre where the climax of history is destined to occur.

Nebuchadnezzar's dream is an intriguing read. Rubenstein is convincing in his premise that many medieval thinkers drew apocalyptic meaning in the success of the First Crusade and the establishment of the Latin Kingdom of Jerusalem. The extent to which this view was shared by the average Crusader and was a driving motivator is less clear, however, and perhaps limited by the available sources. Overall, Rubenstein has added a further dimension to our understanding of the crusades and of medieval apocalyptic thought, and for this his book should be welcomed.