Since the nineteenth century military occupations in Europe have often provoked hostility and opposition among the occupied population. Yet resistance to military occupations occurred for a variety of complex reasons, and is itself a complex phenomenon. There is no single definition of “resistance.” Resistance therefore took numerous forms, from armed resistance to withdrawing labour, from organised action to spontaneous opposition. Hostility to the occupier was often driven by religious, nationalistic or political ideology, as well as the occupier’s own policies. Explaining and defining this complex, perhaps inevitable, phenomenon and gauging its success remains a difficult but fascinating task.