1. The Evolution of British Strategic Policy, 1919-1926. London: Palgrave Macmillan, 1988.
2. The British Army and Signals Intelligence During the First World War (Cheltenham: Army Records Society, 1992).
3. A World History of Warfare (University of Nebraska Press, 2002), with C. Archer, H. Herwig, T. Travers.
4. Intelligence and Strategy, Selected Essays (Oxon: Routledge, 2005).
5. Behind the Enigma: The Authorised History of Britain’s Cyber Security Agency (London: Bloomsbury, 2020).