Warfare itself is changing. Organized violence by nation-states, though still plausible, is diminishing. Instead, unconventional conflicts involving stateless nations, tribes, clans, gangs, ethnic nationalists, and religious fundamentalists are clearly rising. Sooner or later some lethal combination of drug cartels, arms syndicates, international mafias, and terrorist groups will acquire weapons of mass destruction. All of these factors require a more sophisticated understanding of security than that which defined the Cold War.