This book considers the intersections between homeland and international security and the implications of these connections for preparedness. After the terrorist attacks of 9/11, many analysts abandoned traditional strategic tools such as deterrence and dissuasion. Yet policymakers need to consider a range of effective actions to enhance preparedness. The possibility of catastrophic, high consequence events demands that policymakers go beyond piecemeal extensions of current policies and devise comprehensive defense-in-depth. They could develop policy in ""5D"" —by integrating new approaches to five dimensions of policy: deterrence, dissuasion, denial, diplomacy, and defense. The 5Ds could give policymakers ways to ""project resilience"" with others abroad as we build resilience at home.