Although historians have by no means ignored the Second Crusade, it is startling to realise that until now the most recent full-scale history of its three major expeditions was Bernhard Kugler's Studien zur Geschichte des zweiten Kreuzzugs, which appeared almost a century-and-a-half ago. The Second Crusade has of course been the subject of shorter narrative treatments in general histories of the crusades, including those by Stephen Runciman (1951–4), Hans Eberhard Mayer (1965, 1988), Jean Richard (1996) and Jonathan Riley-Smith (1987, 2005). A lengthier account by Virginia G. Berry also appeared in the first volume (1955) of the multi-authored History of the crusades, edited by Kenneth M. Setton. Substantial studies of one aspect or another of this crusade, notably Giles Constable's lengthy article, ‘The Second Crusade as seen by contemporaries’ (1956), have been far more numerous and have added greatly to our understanding of this crusade. In view of the research on the subject since 1866, when Kugler's book appeared, a comprehensive account of the Second Crusade is long overdue and Jonathan Phillips has now set out to supply it.

The term ‘Second Crusade’, despite the fact that it has been hallowed by long use, is really a misnomer. In the aftermath of the First Crusade, the first half of the twelfth century saw numerous military expeditions to the Holy Land, many sanctioned by papal approval, together with crusading indulgences for participants and papal protection for their lands and families, in virtue of canon 10 of the First Lateran Council (1123). Many of these campaigns were relatively small, and none of them even began to approach the size of the armies involved in either the First or the Second Crusades.

After dealing briefly with some of these smaller expeditions, Phillips examines the glowing historical and literary accounts of the successes of the First Crusade that appeared during the decades between 1099 and 1147. These, he argues, produced a wide-spread admiration – at times bordering on veneration – for the heroic deeds of those who had captured Jerusalem and established the Latin States in the Levant. This greatly helped to make it possible for Pope Eugenius iii and Bernard of Clairvaux to envisage recruiting armies on a scale at least roughly comparable to those of the First Crusade with the goal of recovering the Latin county of Edessa, which had fallen under Muslim rule at the end of 1144.

The Second Crusade formally commenced with the promulgation of Eugenius iii's call for a new crusade in the bull Quantum praedecessores at the beginning of December 1145. The pope addressed his appeal in the first instance to the French king, Louis vii, in part, no doubt, because so many of the First Crusade's heroes had come from regions that at least nominally recognised the suzerainty of the French monarchy and in part because he was aware that Louis would be receptive to the idea. He also dispatched further copies to Germany, Denmark, Bohemia, Brittany, Flanders and Spain. Although Phillips does not dwell at length on the later history of Quantum praedecessores, which long remained a major source of crusading ideas and institutions, he does provide a helpful analysis of its principal provisions, as well as a translation of the document in an appendix.

Phillips devotes the following chapter to the launching of the crusade, first at Bourges in December 1145, which turned out to be a false start, then far more successfully at Vézelay at Easter 1146, thanks in part to good advance planning aided by the persuasive powers of Bernard of Clairvaux. A further chapter details St Bernard's commanding role in recruiting troops for the campaign in France, Flanders and Germany. Phillips rightly stresses the importance for the success of recruitment of the fact that the main armies of the Second Crusade, unlike those of the First Crusade, were led by two monarchs, King Louis vii of France and Conrad iii of Germany, both deeply committed to the crusading ideal.

Chapter vi, which studies patterns of response to the recruitment efforts and the motivations of those who enlisted, as well as the financial resources that enlistment in the crusade entailed, is perhaps the most striking and original contribution of Phillips's book. Following the example of Jonathan Riley-Smith in The First Crusaders (1997), Phillips was able to identify slightly more than 350 known participants in the Second Crusade, largely from the evidence of charters, and furnishes a valuable prosopographical analysis of this group. His evidence on the sources from which crusaders secured the resources to support their participation largely reinforces Riley-Smith's findings for the First Crusade. The decision to participate in a crusade was economically irrational, for it not only levied a huge financial toll on the crusader, but was likely to burden his descendants and social networks in future generations as well.

Subsequent chapters provide clear, readable narratives of the expeditions to the Holy Land, as well as those that led to the capture of Lisbon, additional campaigns in the Iberian peninsula, and the abortive expeditions against the Wends and other Slavic groups in northern Germany.

The problem of accounting for the actions of the crusade's leaders during the siege of Damascus has perplexed crusade historians ever since. As political and military considerations ruled out an attack on Edessa, the expedition's leaders decided instead to attack Damascus. After gaining control of the city's western flank, they suddenly moved to the city's eastern edge, only to discover that shortages of food, forage and water there made a siege impractical. The army immediately withdrew and most of its forces soon returned home. Phillips's analysis of the evidence on this puzzling episode, while more nuanced than some, leaves the mystery unresolved.

Despite occasional flaws – notably an apparent misunderstanding of what an indulgence was actually all about – Phillips has done a workmanlike job on a difficult and unwieldy subject.