Under unipolarity, the immediate costs and risks of war are more likely to seem manageable for a militarily dominant power like the U.S. This does not necessarily make the use of force cheap or wise, but it means that the costs and risks attendant on its use are comparatively indirect, long term, and thus highly subject to interpretation. Unipolarity, combined with the opportunity created by September 11, opened a space for interpretation that tempted a highly ideological foreign policy cohort to seize on international terrorism as an issue to transform the balance of power both in the international system and in American party politics. This cohort's response to the terrorist attack was grounded in ideological sincerity but also in the routine practice of wedge issue politics, which had been honed on domestic issues during three decades of partisan ideological polarization and then extended into foreign policy.

In analyzing the current unipolar system, it is useful to begin with structure. No other state or plausible coalition can challenge the unipole's core security, but this does not mean that all its values are safe or that it can get everything that it wants. Contrary to what is often claimed, standard balance of power arguments do not imply that a coalition will form to challenge the unipole. Realism also indicates that rather than seeking to maintain the system, the unipole may seek further expansion. To understand the current system requires combining structural analysis with an appreciation of the particular characteristics of the current era, the United States, and its leaders. Doing so shows further incentives to change the system and highlights the role of nuclear proliferation in modifying existing arrangements.