"The Peacebuilding, Development, and Security (PDS) Program was initiated at the University of Calgary in 2007 with funding from the University Centre for Military and Strategic Studies (CMSS). It represents a partnership between CMSS and the Institute of World Affairs (IWA), based in Arlington, Virginia. The papers republished here expand on presentations made at an expert workshop-- Coordinated Approaches to Security, Development, and Peacekeeping: Lessons Learned from Afghanistan and Liberia-- held in Calgary in March of 2007 by these two organizations. The workshop brought together thirty-five expert practitioners from international assistance agencies, donors, military forces active in Afghanistan and Liberia, along with representatives of the national government and national NGOs to review lessons learned from ongoing international peace operations in the two countries. The aim was to better understand the gap between the policy-level consensus promoting greater aid coordination and coherence in recent years and the actual practice in the field. This issue is significant but little examined, perhaps because it lies at the intersection between traditional conceptions of defence policy, peacekeeping, and the work of NGOs. The Journal of Military and Strategic Studies first published the articles generated from that conference on-line as a topic in its own right under the auspices of the journal's co-editors, John Ferris and James Keeley"--Page [i].