Peter is a Senior Professor of Peace and Conflict Research at Uppsala University, and Richard G. Starmann Sr. Research Professor at the Kroc Institute for International Peace Studies at the University of Notre Dame, USA.

He was Head of the Department of Peace and Conflict Research at Uppsala University from 1972 to 1999 and held the Dag Hammarskjöld Chair from 1985 to 2012. He currently directs the Uppsala Conflict Data Program (UCDP) which continuously publishes free of charge information on global armed conflicts. Peter has published books such as Understanding Conflict Resolution, Peace Research – Theory and Practice, The Go-Between – Jan Eliasson and the Styles of Mediation (with Isak Svensson), and has just finalized Toward Quality Peace: Peacebuilding, Victory and World Order. Peter is presently researching mediation issues with particular focus on Nordic mediators.