•
States of Emergency: British governments and strikebreaking since 1919 (London, 1983) (co-editor with
Peter Hennessy) •
The British Army and the crisis of Empire, 1918–1922 (Manchester, 1984). •
The Military Correspondence of Field Marshal Sir Henry Wilson (Army Record Society, 1985) (Edited). •
Northern Ireland since 1968 (Oxford, 1988) (co-author with Paul Arthur) •
Men, Women, and War (Dublin, 1993) (co-editor with T. G. Fraser) •
A military history of Ireland (Manchester, 1996) (co-editor with Thomas Bartlett) •
An Irish empire? Aspects of Ireland and the British Empire (Manchester, 1996) (editor) •
Ireland and the Great War (Cambridge, 2000) •
The GPO and the Easter Rising (Dublin, 2006) •
Field Marshal Sir Henry Wilson: a political soldier (Oxford, 2006) •
MI6: The history of the Secret Intelligence Service, 1909–1949 (Bloomsbury, 2010) (published in the United States and Canada as
The Secret History of MI6 [Penguin Press, 2010]) •
1916: A Global History (Bloomsbury, 2015) ==See also==