This chapter offers a retrospective analysis of International Disaster Response Law’s (IDRL) evolution in its opening decades, employing the International Federation of Red Cross and Red Crescent Societies’ 2000 policy launch as a pivotal starting point. It emphasizes relief law applicable to weather and geophysically based events. First establishing IDRL’s pre-2000 state, the study highlights recurring field themes and debates enduring over a century. It will then provide the backdrop for IDRL’s emergence in the early twenty-first century as a ‘peacetime’ disaster relief law movement. Next, the study will draw attention to several overarching issues that the Federation has wrestled with since launching its IDRL campaign. Such a focus serves as a constructive prism for appreciating both old and new challenges in the field’s advancement, particularly in light of the global policy conversation surrounding the draft articles on the Protection of Persons in the Event of Disasters.