Population size, structure, distribution, and composition affect security in numerous ways, including national power, civil conflict, and development. _The Future Faces of War: Population and National Security_ offers a comprehensive overview of how demographic trends can function as components, indicators, and multipliers of a state's national security. Each chapter focuses on a particular demographic trend and describes its national security implications in three realms—military, regime, and structural. Illustrating the mechanisms by which demography and security are connected, the book pushes the conversation forward by challenging common conceptions about demographic trends and national security. Key for policymakers and general readers alike, it goes on to suggest ways trends can provide opportunities for building partnerships and strengthening states. Focusing on multiple scenarios and the theoretical links between population and security, the insights gathered here will remain relevant for years to come.