This chapter traces UNHCR’s evolution from a narrowly legal body established in 1950 to a global humanitarian actor. Originally focused on European refugees, its mandate naturally broadened through crises such as the 1956 Hungarian uprising and African decolonisation, incorporating operational duties like shelter, food, and logistics. Formal legal changes, including the 1967 Protocol, mainly formalised practices already in existence. This “mandate expansion by doing” fostered a culture of improvisation, urgency, and responsiveness that shaped organisational identity. However, financial austerity, donor fatigue, and restructuring now expose the fragility of this model, raising important questions about UNHCR’s sustainability, coherence, and capacity to balance flexibility with accountability in a changing global landscape.