This briefing paper summarises shifts in international engagement in South Sudan from humanitarian aid to development and institution-building, and then back again to crisis response. The findings emerge from the recent report, Trajectories of international engagement with state and local actors: Evidence from South Sudan, as well as other SLRC South Sudan research over the life of the programme. In the wake of South Sudan’s Comprehensive Peace Agreement in 2005, optimism abounded that investment in state-building would produce numerous benefits including peace, stability, growth and economic opportunities. But such optimism proved to be unfounded. This paper analyses why current aid frameworks have been mostly unsuccessful in their efforts to promote sustainable institutions and peace in South Sudan. The central argument is that aid actors largely failed because they applied technical solutions to political problems. What is needed is a rethink in approaches, modalities, and time frames, and better use of contextual and political analysis, in order to avoid similar failures in the future.