This article examines the First World War Allied blockade of the Mediterranean, a maritime blockade initiated by Britain and France, later assisted from 1915 by Italy and other Allied powers. It argues that this blockade raises major questions about the ways that the First World War became a ‘total war’, showing wartime radicalisation in the targeting of civilian non-combatants and how this became a war norm. It also argues that the Mediterranean blockade was actually multiple blockades carried out by a range of states, and therefore had a cumulative, wide reach in driving radicalisation, structured around diffuse, multilateral responsibility. This article examines the ways in which the blockade operated, before discussing how it illustrates wartime radicalisation by presenting two case studies on its diverse impact on hospital ships and upon civilians in Lebanon.