- University Academic Fellow, All Souls College (from 2015)
- GF Grant Professor of History, University of Hull (from 2007 to 2015)
- National War College, Washington DC: participation on 6200 War and Statecraft (September 2011)
- MA Summer School and PG workshops, High Point University, North Carolina, USA (June-August 2011)
- Visiting Fellow, Excellence Cluster, University of Münster, Germany (January 2011)
- Professor of Early Modern History, University of Sunderland (from 2001 to 2006)
- Reader in Early Modern European History, University of Sunderland (from 1998 to 2001)
- Lecturer in Early Modern European History, University of Newcastle (from 1994 to 1998)
- Lecturer in Modern European History, University of Sunderland (from 1990 to 1993)
- History of war in wider European and world development from the seventeenth century to around 1900
- Early modern German history, particularly the political, military, social, and cultural history of the Holy Roman Empire between 1495 and 1806
- Iron and Blood: A Military History of the German-speaking Peoples since 1500 (Penguin, 2022; Harvard University Press, 2023). Chinese translation forthcoming with PostWave; Spanish translation forthcoming with Desperta Ferro.
- (edited with Marie Houllemare and Erica Charters), A Global History of Early Modern Violence (Manchester University Press, 2020).
- Lützen (Oxford University Press, 2018).
- The Holy Roman Empire: A Thousand Years of Europe’s History (Penguin, 2016) published in the US by Harvard University Press as The Heart of Europe: A History of the Holy Roman Empire (2016). Chinese translation forthcoming with Citic (2018). Italian translation with Il Saggiatore (Milan, 2018). Spanish translation in preparation (Desperta Ferro, 2020).
- (with Robert Evans) The Holy Roman Empire, 1495-1806: A European Perspective (Leiden: Brill, 2012).
- (with Robert Evans and Michael Schaich) The Holy Roman Empire, 1495-1806 (Oxford: Oxford University Press, 2011).
- The Holy Roman Empire 1495-1806 (Studies in European History Series) (entirely revised 2nd ed., Basingstoke: Palgrave, 2011).
- The Thirty Years War: A Sourcebook (Basingstoke: Palgrave, 2010).
- Europe’s Tragedy: A History of the Thirty Years War (London: Allen Lane/Penguin, 2009). Also published as The Thirty Years War: Europe’s Tragedy by Harvard University Press, 2009. Polish translation with F.H.U. Napoleon V Dariusz Marszalek (Oswiecim, 2017); German edition (Theiss, 2017); Spanish edition published in two volumes by Desperta Ferro Ediciones (2018); Chinese translation forthcoming with Post Wave (Beijing); Macedonian translation forthcoming with ARS Studio, sponsored by the Macedonian Ministry of Culture.
- (with Alan Forrest) The Bee and the Eagle: Napoleonic France and the end of the Holy Roman Empire, 1806 (Basingstoke: Palgrave, 2009).
- A Companion to Eighteenth-Century Europe (Oxford: Blackwell, 2008; paperback edition 2013).
- Warfare in Europe 1815-1914 (International Library of Military History) (Aldershot: Ashgate, 2006).
- 1848. The Year of Revolutions (International Library of Essays in Political History) (Aldershot: Ashgate, 2006).
- From Reich to Revolution: German history 1558-1806 (Basingstoke: Palgrave, 2004).
- Absolutism in Central Europe (Historical Connections Series) (London: Routledge, 2000).
- The Holy Roman Empire 1495-1806 (Studies in European History Series) (Basingstoke: Macmillan Press, 1999; New York: St Martin’s Press, 1999); Chinese translation (Beijing: Peking University Press, 2013); Japanese translation (Tokyo: Iwanami Shoten Publishing, 2005).
- German armies: War and German politics 1648-1806 (London: UCL Press, 1998).
- War, state and society in Württemberg, 1677-1793 (Cambridge Studies in Early Modern History) (Cambridge: Cambridge University Press, 1995).
- Principal Investigator on the European Fiscal Military System 1530-1870 project 2018-25
- Scientific Advisory Board, Institute of Habsburg and Balkan Studies (IHB), Vienna
- Editorial Board, War and Society
- War in seventeenth to nineteenth century world history
- Social, cultural, political or military history of German-speaking Europe
- European history 1500-1800
- European Research Council Advanced Grant award (2018-23) for the European Fiscal-Military System 1530-1870: https://fiscalmilitary.history.ox.ac.uk/.
- Holy Roman Empire named one of the Best Books of 2016 by The Economist, The Daily Telegraph and Waterstones.
- 'The causes of the Thirty Years War 1618-48' named one of the English Historical Review’s '35 most respected articles' (2011).
- Society for Military History Distinguished Book Award for Europe’s Tragedy (2011).
- Europe’s Tragedy named Paperback of the Week by the Sunday Times, 11.7.10 (2010).
- Europe’s Tragedy named a Book of the Year by the New Statesman and The Atlantic, a Best History Book of the Year by The Independent, and a Choice Outstanding Academic Title of the Year
(2009).