The chapter explores the ways in which, and the reasons why, humanitarian discourse in disarmament was marginalised in the first two decades following the Second World War. The chapter starts by providing a brief overview of the way in which weapons technology developed in advance of and during the Second World War, looking in particular at anti-personnel landmines, incendiary weapons, major developments in aerial warfare and nuclear weapons. It also identifies reasons why the overall environment was so resistant to humanitarian disarmament in this period, including a possible desensitisation to the harms wrought by the War, the security rather than peace focus of the new United Nations and the way in which humanitarianism itself became institutionalised and therefore politically suspect. Despite the inhospitable environment, important efforts were made through the work of the International Committee of the Red Cross to regulate the use of indiscriminate weapons through its attempt to persuade states to adopt various rules against particular types of weapons and means of warfare. Although ultimately unsuccessful, this campaign was a clear attempt to use humanitarian arguments to support calls for legal prohibitions on the use of certain weapons.