This book provides the first comprehensive history of the American Friends Service Committee (AFSC), the central aid agency of Religious Society of Friends or Quakers, from 1917 to 1939. Implying a thoroughly transnational approach, it sheds a light on the important role American Quakers played in the emergence of a humanitarian sector within the USA and beyond. Through the Quaker lens the book adresses important tensions inherent to the history of humanitarianism in the 20th century: Following the AFSCs aid operations from the First World War, through post-war Germany and Soviet Russia to the Spanish Civil War it deals with the AFSC's conflicting roles as a specifically American aid organization on the one hand and its position within transnational religious and pacifist networks on the other and it opens a window to processes of professionalization, the development of humanitarian techniques and the complex relationship of religious and secular strands in the history of humanitarianism.