Fire as a management practice in South Africa’s grasslands inflamed heated debate throughout the twentieth century. Imported ecological ideas meshed with homegrown sectoral land management traditions to reinforce a powerful anti-burning narrative among experts. Farmers, however, developed their own theories on burning, and the history of fire research, policy, and management reveals a series of entanglements between ecological theory, management policies and recommendations, and practice that complicate narratives grounded in historiographical traditions focused on critiquing settler and colonial expertise. This article recommends three distinctions to make when thinking about the history of scientific expertise: first, between an individual’s abstract theorizing and his or her “thinking in the field”; second, between the influence of accepted scientific findings and the thinking guiding official policies of land management sectors; and third, between official policies and actual land management practices. This article provides overviews of long-term fire use in the country’s grasslands, the ecology of grasslands and fire in South Africa, of early debates over fire, and scientific fire research and management in the country.