The Israeli destruction of Gaza has returned the idea of genocide to the centre of world politics, with sharp conflicts between protesters and international lawyers who invoke it and Western governments and media that deny it. The idea has now been part of global politics and intellectual life for eighty years, but attitudes to it have waxed and waned according to political circumstances and intellectual fashion, with its meaning becoming unclear and contested. Recently, influential thinkers have argued that the term has become redundant. This book, by the foremost sociological theorist of genocide, defends the concept and argues that in the current period it is urgent to make it more coherent, restoring it to a central place in thinking about mass atrocities. Examining genocide in Gaza, in the Russian attempt to eliminate Ukraine, and the longer histories of Palestine and British complicity, together with the problem of 'political groups' as targets, this book brings the debate up to date and is essential reading for all concerned with the problem.