The word 'hostage' might immediately bring to mind hostile situations: the entrapment of a wealthy businessman's daughter in exchange for money, a terrorist incident (1) or a manifestation of domestic abuse. (2) However, the meaning of hostageship has undergone many transformations over time, some of which are brought under the microscope Professor Adam Kosto as he dissects the development of this phenomenon during the Middle Ages. In attempting to emphasise the distinction between the modern perception of hostageship and that of the medieval era, Kosto argues that in the past hostageship was seen as not simply a legal issue, but also as a political one. This distinction between the modern sense of the term and the medieval one is something Kosto continually addresses in his bid to avoid the historian's most cardinal sin, anachronism. The pitfalls of linguistic interpretation in history are evident and Kosto is very good at putting the medieval usage of 'hostage' in context. However, aside from a few pages at the end of the book (p. 220-6), he seems to overlook the modern use of the term and only makes reference to it, briefly, in terms of the Hostage Convention of 1979, the US Lieber Code or the Nuremberg Trials. Kosto somewhat understates the variety of modern hostageship and could have emphasized this further. But essentially, this is a deeply historical investigation and the parts of the book where it deals with the modern period are not central to its thesis. Drawing on the work of Ascan Lutteroth, Kosto also identifies the modern distinction between hostages forcibly taken and hostages given as a result of negotiation, which has been seen as a product of modern international law (p. 5), although it also existed in an exceedingly multi-facetted way in the Middle Ages. The author is very clear in his claims: firstly, medieval hostageship was not only a guarantee as such, but was firmly embedded in contemporary politics. Secondly, as society changed, so did the nature of hostageship. And finally, despite the societal progress made in key areas such as law and governance, 'physical control over people remained crucial' in the politics of this time, though one also sees international law and economics coming to the fore. In first providing a general overview of the history of hostages, hostage precursors are revealed in Rome and Persia, and even pre-Islamic Arabia. Nonetheless, the Middle Ages are selected as the main focus of this book, due to the practice of hostageship being at its peak in this period and, as the author puts it, featuring in