During the Cold War era, it was considered dangerous for states not to respect one another's sovereignty. Since that time, however, the United States has developed a virtual monopoly on the dominant means of military power in the world and has begun to use that power both to regulate relations among subordinate dependent states and to ensure that there are governments within those other nations that are acceptable to us.

The key way in which empires differ from ordinary powerful states is that they do not respect the sovereignty of other countries. Empires reach out and impose minimally acceptable domestic political systems in other nations, usually through indirect rule. The United States has been doing this for some time, first in Latin America and, since the end of the Cold War, more broadly.

In many parts of the world, the U.S. has no military rival. In fact, the U.S. Defense Department spends more than twice as much on research and development alone as the entire French defense budget. And that means the American dominance in military power is likely to persist and extend into the future as we continue to build the knowledge, technical infrastructure, and capacities we've been generating for more than half a century. Moreover, the U.S. excels in training military personnel--the level of competence and professionalism among our 19- and 20-year olds military personnel is astounding.

The combination of this human capital with American economic and technological strength can easily defeat conventional military power, as was demonstrated in Afghanistan and Iraq. Indeed, since the Clinton administration, we have been using this formidable combination to go inside other countries--such as Somalia, Bosnia, Kosovo, and Haiti--to tell them how they should live. We didn't ask these governments for permission to intervene in their countries; we just did it. This is how an empire acts.