In this important study David Armstrong examines the impact of revolutionary states on the international system. These states have always posed major problems for the achievement of world order: revolution is often accompanied by international as well as civil conflict, while revolutionary doctrines have proven to be highly disruptive of the existing structure of international politics. Dr Armstrong asks whether revolutionary states are `socialized' into adopting acceptable patterns of international behaviour or whether it is international society that is forced to change when these new states appear. He looks in detail at the French, American, and Russian revolutions and at several post-1945 revolutionary states; he also examines the relationship between revolutionary states and the principal ordering devices of international society: international law, diplomacy, and the balance of power. His book is a major contribution to international relations and an important development and application of the `international society' concept.