This introductory article surveys four decades of work on peace, security, and development, centring on articles published in previous issues of the IDS Bulletin. These articles focused initially on disarmament and its actual and potential contributions to development. After the end of the Cold War, development research engaged more and more directly with conflict prevention and peace-building, turning the spotlight upon security. IDS work has been distinctive in three respects. First, in interrogating the multiple meanings of security, delinking it from state and international security. Second, by tracing the complex links between global, national, local, and personal security. Third, in its insistence that security be inclusive, drawing upon the experience and agency of the people and groups who are ‘developed’ and ‘secured’.