Despite being more akin to a cultural history or perhaps even a genealogy of the Third Crusade than a traditional military history, this book grew out of my interest in unit cohesion, or the bonding together of warriors in a military organisation to sustain them in combat. In particular, it was inspired by Jan-Frans Verbruggen's view that the Règle du Temple was in part an attempt to replicate the bonds found in lay military households, which were arguably based on established social bonds – on family and locality. However, the base assumption on the composition of lay households required, in my view, more investigation before it could be safely used to consider this question.

Recent debate on unit cohesion has featured a distinction between the components of social cohesion and task cohesion – the commitment to working together on a shared goal. Since some studies have concluded that unit effectiveness is determined more by task cohesion than social cohesion, I thought it important to focus on a period in which various households from across Christendom were brought together for a common goal, such as in the attempted reconquest of the kingdom of Jerusalem.

Like any such endeavour, researching and writing this book has benefited from the support of various bodies, as well as the goodwill and generous help of my own kinship and friendship network. Though it is impossible to repay many of the debts incurred, it is my pleasure to recognise them and to publicly offer my thanks for the help I was given during this project. Among the many debts of gratitude to individuals that I have incurred over the years whilst researching and writing this book the first is due to Tom Asbridge, who throughout the whole time has been an unfailing source of wisdom and support. Without his diligent guidance and unceasing encouragement, this may have stalled early on. I wish to express my profound thanks to Matthew Bennett for his keen insights and encouragement throughout the process. Similarly, I am also grateful to Caroline Palmer, Judith Everard, and Nick Bingham for their patience and support.