- 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). Winner of the Wellington Medal for Military History 2023. Chinese, German, and Spanish translations.
- 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, Italian, and Spanish translations. Korean translation in preparation. The Economist and Telegraph Book of the Year.
- The Holy Roman Empire 1495-1806 (Studies in European History Series) (entirely revised 2nd ed., Basingstoke: Palgrave, 2011). Chinese translation in preparation.
- 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. Chinese, German, Macedonian, Polish, and Spanish translations. Society of Military History Distinguished Book Award 2011.
- 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).