Military Simulation & Serious Games is a collection of essays on the technical, social, and economic importance of simulation and gaming techniques, tools, and technologies. It provides a fascinating historical summary, explores important technical capabilities, and speculates on the role that these technologies will play in the future. Simulation has been a powerful tool for training the military for over 3000 years. What began as sand tables and board games has evolved into advanced computer and communication systems that encompass the globe and provide training portals on every continent. Commercial computer games have followed a similar evolutionary trajectory in delivering entertainment. The core technologies behind both fields have many commonalities which become more intertwined every year.