Why do some armies fare better than others on the battlefield? In Divided Armies: Inequality and Battlefield Performance in Modern War (Princeton UP, 2020), Jason Lyall argues that a state's prewar treatment of ethnic groups within its population determine subsequent battlefield performance. Treating certain ethnic groups as second-class citizens, either by subjecting them to state-sanctioned discrimination or, worse, violence, undermines interethnic trust, fuels grievances, and leads victimized soldiers to subvert military authorities once war begins. The author tests this argument using Project Mars, a new dataset on conventional wars fought since 1800. Combining historical comparisons and statistical analysis, he also marshals evidence from nine wars, ranging from the Eastern Fronts of World Wars I and II to less familiar wars in Africa and Central Asia, to illustrate inequality's effects. Divided Armies was awarded the 2021 Peter Katzenstein Book Prize, the 2020 Joseph Lepgold Prize, and was named a "Best of 2020" book by Foreign Affairs.

Jason Lyall is the inaugural James Wright Chair of Transnational Studies and Associate Professor in the Government department. He also directs the Political Violence FieldLab at the John Sloan Dickey Center for International Understanding. His research examines the effects and effectiveness of political violence in civil and conventional wars. His research has been published in the American Political Science Review, American Journal of Political Science, International Organization, Journal of Conflict Resolution, Journal of Peace Research, Journal of Politics, and World Politics, among others. He has received funding from AidData/USAID, the Air Force Office of Scientific Research, the MacArthur Foundation, the Folke Bernadotte Academy, and the United States Institute of Peace. He has conducted fieldwork in Russia and Afghanistan, where he served as the Technical Adviser for USAID's Measuring the Impact of Stabilization Initiatives (MISTI) project during 2012-15. He was named an Andrew Carnegie Fellow in 2020.

Aditya Srinivasan assisted with this episode.

Lamis Abdelaaty is an assistant professor of political science at the Maxwell School of Syracuse University. She is the author of Discrimination and Delegation: Explaining State Responses to Refugees (Oxford University Press, 2021). Email her comments at labdelaa@syr.edu or tweet to @LAbdelaaty.