The year 2024 marks the 20th anniversary of the Indian Ocean earthquake and tsunami. On 26 December 2004, a major earthquake struck with its epicentre off the west coast of northern Sumatra, Indonesia. The impact of the tsunami was a wakeup call to the world to pay greater attention to disasters, review and reform disaster management and emergency response, and improve cooperation in times of crises.Over the past two decades, the global humanitarian system has undergone significant developments stemming from the increasing scale, frequency, and complexity of disasters, as well as changing political contexts. The contributors to this volume provide important insights drawing on their professional and research experience to understand the roles, motivations, and challenges in the humanitarian community from a diverse range of civilian and military perspectives.