He studied history, philosophy and music in Berlin, Paris, Berkeley and Florence. After teaching at Oxford and Lyon, he is currently professor of modern history at the University of Normandy in Caen (France). His publications include Citizens, Soldiers and National Armies: Military Service in France and Germany, 1789-1830 (Routledge 2007), Bombing the People: Giulio Douhet and the Foundations of Air Power Strategy, 1884-1939 (Cambridge University Press 2013), Paradoxes of Peace in Nineteenth Century Europe, co-edited with Milos Vec (Oxford University Press 2015) and Governing from the Skies: A Global History of Aerial Bombing (Verso 2017). He is currently involved in a research project on the conceptual history of peace at European and global level.