We are a small team of committed Thirdsiders dedicated to transforming the way the world makes peace. 

If not us, who?
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Bestselling author, and co-founder of Harvard’s Program on Negotiation, William Ury has spent the past 45 years helping individuals, organizations and nations at war get to YES. 

William is one of the world’s leading experts on negotiation and mediation. He is co-author of Getting to YES, a sixteen-million-copy bestseller translated into over thirty-five languages, and the author of Getting Past No, The Power of a Positive No, The Third Side, and, most recently, the award-winning Getting to Yes with Yourself


William has served as a negotiation adviser and mediator in conflicts ranging from wildcat coal mine strikes to boardroom battles to ethnic wars in the Middle East, Africa, the Balkans, the Caucasus, and Indonesia. Together with President Jimmy Carter, he co-founded the International Negotiation Network aimed at resolving civil wars around the world.  In recent years, he has served as a peace advisor to President Santos of Colombia and President Ghani of Afghanistan.

A lot of people ask me after all these years of working on war, are you an optimist or pessimist? I like to answer that I’m actually a Possibilist. I believe in human potential…


William Ury

My purpose here is to share the art of Possibilism with you so that together we can help make our world safer and happier for all.


Meet The Team


Managing Director

Robert Sokol


Rob Sokol joined OEF as the Managing Director of the eXperimental Negotiation Initiative (xNI) in early 2022.  His role is to build and scale xNI’s international conflict negotiation and training practices with the goal of awakening human capacity to transform the most difficult conflicts into creative negotiations.  He comes to OEF from Trinity Wall Street, where he served as the Chief Administration Officer. Before that, Mr. Sokol served as the Chief Operating Officer at the Washington National Cathedral. And before that, he served in the Office of the Librarian at the Library of Congress as the Creative Director, among other roles. Mr. Sokol received his Humanities and International Relations degrees from Seattle University and Nanjing University (China), with foci on economics and Chinese history. He lives in Washington DC with his wife and two boys, both in grade school.  Other than spending time with his family, his favorite pastimes are swimming and photography.


Associate Director, Programs

Liza Hester


Liza Hester is a Program Manager with xNI, where she helps catalyze and equip “SWAT Networks” in intractable conflicts around the globe. She received her M.A. in Conflict Resolution from the Josef Korbel School of International Studies at the University of Denver. Her graduate studies focused on the intersections between psychosocial health and peacebuilding in protracted conflict.


Conflict Fellow

Daniel Medina


Daniel Medina is Conflict Fellow at Side3, where he supports the Conflict Portfolio research and the team´s community engagement. He is a Political Scientist from Bogotá, Colombia, with an M.A in Peacebuilding and an M.S. in Negotiation and Conflict Resolution from Columbia University (2022). His background has developed around peace research and political communication.


Deputy Director

Gia Medeiros


A storyteller and entrepreneur, Gia has spent the past 20+ years providing strategy, innovation and organizational development consulting to purpose-driven organizations large and small. She is now working with OEF to grow xNI, bringing innovation to negotiation by disseminating breakthrough methods to the peacemaking field.


Program Coordinator

Olivia Grotenhuis


Olivia Grotenhuis is Project Coordinator at xNI, where she actively tracks and supports xNI's conflict portfolios - with an emphasis on North Korea, Afghanistan, Venezuela and climate change - as well as provides logistical and administrative support on day to day operations. She received her B.A. from the University of Virginia in foreign affairs and East Asian Studies with a concentration in Korean language.