Peter Turchin may not think I am the ideal reviewer for his War and Peace and War, for I am a political historian of the most conventional type, with most of my research being in the modern period and concerned with the British Empire. He is professor of ecology and evolutionary biology, and a serious mathematician to boot, whose main concern in this book is to analyse the pre-industrial land-based European superstates to find out why some nations build successful empires and others do not. And why, inevitably, even the successful eventually go into decline. On the other hand, he is, as his publisher claims, presenting" cliodynamics, the new science of history, to general readers for the first time" and has" rewritten the history of the world", so I suppose there is some justice in a review of his book from an old-fashioned historian, even if it is someone whose mathematics barely reaches O-level algebra.

Turchin's scholarly reputation has rested hitherto on the application of mathematical theory and statistical modelling to various sorts of ecosystems-for example, how populations of larch budmoth or red grouse, or voles, lemmings, hares and ungulates, go through various definable cycles in relation to their size and the physical environments in which they are located. He finds a clear relationship between the size and structure of populations and their ability to reproduce within a given context. In the right environment, populations grow; but at some point the pressure on resources precipitates catastrophic decline. Decline again alters the balance and permits a new phase of growth and expansion, so there is a recognisable and trackable (though not necessarily predictable) life cycle for all living things.