Security and stability in the 21st century have little to do with traditional power politics, military conflict between states, and issues of grand strategy. Instead they revolve around the disruptive consequences of globalization, declining governance, inequality, urbanization, and nonstate violent actors. The author explores the implications of these issues for the United States. He proposes a rejection of "stateocentric" assumptions and an embrace of the notion of the New Middle Ages characterized, among other things, by competing structures, fragmented authority, and the rise of "no-go" zones. He also suggests that the world could tip into a New Dark Age. He identifies three major options for the United States in responding to such a development. The author argues that for interventions to have any chance of success the United States will have to move to a trans-agency approach. But even this might not be sufficient to stanch the chaos and prevent the continuing decline of the Westphalian state.