Diplomatic Investigations is a classic work in the field of International Relations. It is one of the few books in the field of International Relations (IR) that can be called iconic. Edited by Herbert Butterfield and Martin Wight, it brings together twelve papers delivered to early meetings of the British Committee on the Theory of International Politics, including several classic essays: Wight's 'Why is there no International Theory?' and 'Western Values in International Relations', Hedley Bull's 'Society and Anarchy in International Relations' and 'The Grotian Conception of International Society', and the two contributions made by Butterfield and by Wight on 'The Balance of Power'. Individually and collectively, these chapters have influenced not just the English school of international relations, but also a range of other approaches to the field of IR. After Diplomatic Investigations ceased to be available in print, it became a highly sought after book in the second-hand marketplace. This reissue, which includes a new introduction by Ian Hall and Tim Dunne, will ensure the book is available in the normal way, thereby enabling new generations of students and scholars to appreciate the work.