Investigating the origins of aid work in Britain, this article examines the formation of humanitarian relief as a new field of vocational endeavour distinguished by an ethos of “rational compassion”. It analyses the competing grounds for intervention produced by the rival British National Society for Aid to the Sick and Wounded in War and the Quaker Friends’ War Victims’ Relief Fund in the Franco-Prussian War, and the alternative meanings and moral investments made in the increasingly systematised administration of relief. In doing so, it utilises organisational papers and the first-hand testimony of relief workers to document the development of novel relief practices and roles that have received little historical attention.