This is a background paper to give a broad overview of the literature and debates in the field of state building. The aim is to bring insights from a developmental states perspective to bear on the challenges of state-building in fragile and post-conflict states; and to explore some of the challenges for why externally supported state-building has not led to expected results in a number of cases. The paper informs the donor, DFID, in drawing together conclusions about the main lessons for the future in terms of how to approach state building.