Primacy is more likely to address terror threats—multiple reasons

We have shown that the grand strategy yields a net gain in security that is favorable to US national interests and a major increase in opportunities for interstate cooperation. Both of these outcomes are hugely consequential for addressing terrorism and other forms of nonstate violence. A more violent and unstable interstate setting would arguably increase the incentives, opportunities, and capabilities of terrorist organizations. Even if the terrorist challenge did not increase, the task of effectively addressing it would be immeasurably harder and more complicated if the United States simultaneously had to grapple with a much more challenging and threatening interstate strategic setting than the one it faces today. By helping to keep that world at bay, deep engagement’s security alliances are an important part of counterterrorism strategy. Moreover, the clear verdict of scholarship is that those alliances enable far more, and far more efficient, intergovernmental cooperation in the fight against terrorism than would occur in a less institutionalized setting without a clear leading state. The grand strategy would only contradict rather than complement the struggle against terrorism if it could be shown to exacerbate terrorism or cause terrorists to direct their attention to the United States. In chapter 8 we demonstrated that this objection is unwarranted: there is no evidence that deep engagement’s forward-leaning military posture in Asia and Europe generates anti-US terrorism. And in the Persian Gulf deep engagement does not require a major onshore military posture of the type most worrying to some terrorism specialists. Moreover, because critics of deep engagement still wish to retain the ability to undertake massive military interventions in the region if necessary, the military postures they recommend do not diverge from deep engagement as much as it may seem. There is no theoretical or empirical basis for concluding that differences of this scale would affect the disposition of actors like al-Qaeda and ISIS/ISIL toward the United States.