What is genocide, and why does the world have so much difficulty identifying where and when it occurs? The world often has been powerless to stop genocide–from the atrocities committed by the Khmer Rouge in Cambodia and the Nazis in Europe to slaughterings of Tutsis in Rwanda and ethnic cleansing in Bosnia–in its tracks. At a Thinking L.A. event co-presented by UCLA, UCLA Burkle Center for International Relations Director Kal Raustiala talked with UCLA historian Richard G. Hovannisian, University of Wisconsin political scientist Scott Straus, World Peace Foundation research director Bridget Conley-Zilkic, and Sudd Institute co-founder Jok Madut Jok about what instigates the mass killings of certain groups of people–and how these acts of brutal violence can be prevented.