Peter Biar Ajak is a postdoctoral fellow in the Belfer Center's International Security Program. His research focuses on understanding the evolving trajectories of state formation in South Sudan. Dr. Ajak was previously a Visiting Fellow and Adjunct Faculty at the Africa Center for Strategic Studies of the National Defense University and a Reagan-Fascell Democracy Fellow at the National Endowment for Democracy, where he was later a Visiting Fellow. He was also a Senior Advisor to South Sudan's Minister of National Security in the Office of the President of South Sudan from 2011–2013. He was later detained in South Sudan’s notorious "Blue House" from 2018–2020 for his fervent advocacy of free and fair elections in South Sudan.

His book project focuses on how internal dynamics within the rebel Sudan People's Liberation Movement / Army (SPLM/A) shaped its exercise of authority and created patterns of behaviors that were replicated during peace time and which explain South Sudan's state formation. Dr. Ajak is an Archbishop Desmond Tutu Fellow at the African Leadership Institute, a Millennium Fellow at the Atlantic Council, and a Young Global Leader at the World Economic Forum. He holds a B.A. in Economics from LaSalle University, a Master of Public Administration in International Development (MPA/ID) from Harvard Kennedy School, and a Ph.D. in Politics & International Studies from the University of Cambridge.