The Hospitallers were a religious order, founded in Jerusalem by 1099, devoted to nursing and to fighting the infidel. With their fellow knights, the Templars, they played a heroic part in the defence of the Holy Land, defending great castles, such as Krak des Chevaliers, while at the same time providing exemplary nursing care for the poor. Hospitallers is an illustrated history, by a leading historian of the crusades, of this remarkable body, the heir of which is the Order of St. John.

This short study of the history of the Order of St John of Jerusalem, Rhodes and Malta, also known as the Knights Hospitaller, is intended as an introduction to the Order for academics working in other fields, as well as the interested general reader. Beginning with a consideration of the origins of the Order as a hospice for pilgrims in Jerusalem in the eleventh century, it traces the Hospitaller's development into a military order during the first part of the 12th century, and its military activities on the frontiers of Christendom in the eastern Mediterranean, Spain and eastern Europe during the middle ages and into early modern period: its role in crusades and in wars against non-Christians on land and at sea, as well as its role in building and maintaining fortresses.