OR, Defence and Security presents eleven papers, originally published in the Journal of the Operational Research Society and the Journal of Simulation, which exemplify important themes and topics in Operational Research (OR), as applied to modern-day defense and security issues. Topics range from frontline OR in a peace-support operation to new developments in combat modelling, and from the logistics of overseas intervention to defence planning at the top level. Also included are examples of applications addressing insurgency and terrorism. Edited by Dr Roger A. Forder, who had a distinguished career in OR in the UK Ministry of Defence, he has also written an authoritative introductory chapter which sets the papers in the context of the global strategic environment as it has evolved since the end of the Cold War. The OR Essentials series presents a unique cross-section of high quality research work fundamental to understanding contemporary issues and research in across a range of Operational Research (OR) topics. It brings together some of the best research papers from the esteemed Operational Research Society and its associated journals, also published by Palgrave Macmillan.