Cato Institute vice president for defense and foreign policy studies Christopher Preble—who I consider myself fortunate to call both a friend and mentor—had a piece in The National Interest last week responding to my recent paper on libertarian foreign policy. I’m not at all surprised it is a thoughtful response and one well worth reading. Chris states right from the outset that in disagreeing with my argument he is not suggesting that his preferred foreign policy is the “correct” libertarian foreign policy. And I agree, for the most part because I don’t assume my proposal represents the “correct” libertarian foreign policy either. (I’m skeptical such a thing actually exists.)

In fact, one of the most striking things about Chris’ response is how much we agree. Both of us seek a more peaceful American foreign policy. At the same time, we are both concerned about the damage perpetual warfare does to a free society.

I think we get to the nub of our disagreement in a theme Chris returns to several times in the article but is perhaps best summed up here:

It all comes back to how many wars the nation fights, and for what purpose. And the United States fights more wars under deep engagement than it would if it adopted a more restrained foreign policy, and far more than it did throughout most of history. My colleague John Glaser estimates that the United States has fought more wars in the last twenty-eight years than it did in the first 190 years.

Later in his piece, citing the larger military force structure required if the United States does not shed its current alliances, Chris argues, “But maintaining a massive national-security apparatus in anticipation of an uncertain tomorrow is a threat to limited government and individual liberty today.”

Where Chris and I part ways is that I don’t believe the type of political-military retrenchment he and many other libertarians envision actually solves these problems. As I discuss in my paper, whether one believes a more “restrained foreign policy”—one in which the United States exits its alliances with many of the world’s major powers—will actually lead to fewer wars depends on a number of assumptions that I think require further examination.

The decline in interstate warfare that scholars such as Steven Pinker and John Mueller have written about is a welcome development. And it may continue as powerful states in Europe and Asia that are currently allied with the United States once again provide for their own security. Perhaps economic interdependence and norms against military aggression will prove robust. But the same international relations’ school of thought that provides the justification for a foreign policy retrenchment highlights a number of risks that suggest a world that might be far less peaceful than the one we see today. If that happens, the risk that the United States could become involved in major wars—and the risk of the state growth and oppression that accompanies such wars—is likely to increase.

We don’t actually know whether the United States, or the rest of the world, for that matter, will be at war less frequently if America retrenches. It will require a natural experiment to find out. Given the risks involved in such an experiment though, the benefits retrenchment provides for a free society should be substantial.

But as I discuss in the paper, retrenchment does not really address the threat a “massive national security apparatus” poses to a free society. Should the United States jettison its security commitments, it can reduce its military force structure. As Chris and others have shown elsewhere, doing so would produce financial savings. To the degree that those savings lead to fewer financial resources being extracted from individual Americans, it would be a step toward a freer society. But those savings could also be wiped out if the world becomes more competitive in the absence of American security guarantees and the chances of war increase, requiring the United States to regenerate the military power it previously discarded.

But even if those financial savings could be achieved, the national security state would remain “massive” under retrenchment. The U.S. military’s force structure would be smaller, but its active-duty end-strength would shrink to just under 1 million from 1.3 million. The surveillance state and aspects of the intelligence community dedicated to fighting terrorism also would remain even if the United States decides to leave NATO. That apparatus will continue to pose a threat to a free society even if American grand strategy is no longer oriented toward anticipating an uncertain tomorrow.

Moreover, getting out of NATO or America’s alliances with Japan and South Korea does little to stop limited U.S. military interventions elsewhere in the world. For example, Chris and I both agree that terrorism is a minor threat that does not require a major military response. But not everyone agrees with that proposition. And even with a reduced military force structure, a “light footprint” approach to counterterrorism using drone strikes and special operations forces will remain quite possible and can still lead to a great deal of misery abroad.

Perhaps a president willing to pursue a grand strategy of “restraint” will share the same skepticism about the urgency of the terrorist threat as Chris and I do, but he or she will have only two terms in office. The pacifying effect of retrenchment is therefore really contingent on the continual election of presidents who share a similar threat perception. But even beyond counterterrorism, the U.S. military’s force structure following retrenchment will retain the ability to project power globally and American leaders will therefore retain the ability to use military force for a variety of reasons unrelated to a narrowly construed idea of national self-defense.

So what we are really debating here is means rather than ends. Chris and I both want to see the United States adopt a more peaceful foreign policy abroad, and a free society flourishing at home. We differ on whether exiting America’s alliances will increase the likelihood of war by the world’s major power, produce significant benefits for a free society, or inhibit the tendency of American leaders to use military force. But in the end, these matters are up for debate. And I (yet again) agree with Chris that such a debate is healthy for both libertarians specifically and for American foreign policy more broadly. It’s a debate I look forward to continuing!