This White Volume assesses U.S. long term national security challenges, employing a global perspective that accounts for the changing political, economic, social, and psychological profiles of populations, and the rapid changes they experience in a globally connected information environment. It addresses many of the key national security challenges identified by LTG Flynn in the Preface. The collection of essays explores future population-centric national security challenges through the lens of the latest research from the social, neurobiological, and complexity sciences. The papers emphasize "enduring" long term theses that are focused on the interactions of populations and their environments. They are not U.S.-centric, but multi-perspective and examine underlying long term phenomena. The target audiences are planners, operators, and policy makers. With them in mind, the articles are intentionally kept short and written to stand alone. All the contributors have done their best to make their articles easily accessible.