Whilst historians and historical geographers have offered much to scholarship concerning military geographies, rarely have military mobilities been at the forefront of these enquiries. Where scholars have considered the movements that underscore military activities (within and beyond the theatre of war) movement is frequently taken to be the straightforward motion of people, equipment, vehicles and so on, from point A to B. This paper opens the special issue on ‘Military mobilities in an age of global war, 1870–1945’ by outlining the role that scholarship on mobility can play in understanding military operations and activities. It focuses on a number of military mobilities, examining how different technologies, knowledges, infrastructures and mobile embodied practices have been vital to military operations. Centred around four themes – military ‘moorings’ and ‘hubs’ military movement spaces; the work of military geographers on movement; and the movement of military bodies – this paper demonstrates how mobilities literature and historical geographies may intersect and inform one another. The paper closes by introducing the four papers which focus on the increasing mechanisation and mobilisation of military forces between 1870 and 1945.