Fifty Years of Operations Research in Defense

The OR (Operations Research) in defense literature is reviewed. Various OR methodologies are outlined, e.g. decision theory, game theory, mergers of differential equations and game theory, and adversarial risk analysis. What is being defended is specified, warfare is described, and common tools and characteristics of the literature are illustrated. The literature is reviewed by classifying it as follows. The system structure of what is being defended is classified into single target, series systems, parallel systems, series-parallel systems, networks, multiple targets, interdependent systems, degraded systems, and other types of systems. Defense strategies are classified into protection, redundancy, false targets, separation of system targets, individual versus overarching defense and, special versus general protection and attack, proactive versus reactive defense, and defending with negative or positive incentives. Attack strategies are classified into attack against a single target, attack against multiple targets, consecutive attacks, and random attack. Defense and attack circumstances are classified into combination of intentional and unintentional impacts, incomplete information, information sharing, cyber war, variable resources, expendable versus nonexpendable resources, multiple defenders, multiple attackers, and multiple defenders and multiple attackers. Reflections are provided on open problems, gaps between the current state of research and real world needs, and prospective research directions.