The dominance of liberal norms and the prevalence of democracy and free-market capitalism around the world have direct, practical, and positive security implications for the United States. “Today, the world’s great industrial powers share similar democratic national identities and appear to eliminate the balancing of military power from their relationships altogether,” according to Henry Nau, a scholar and former Reagan administration official. Similarly, John Ikenberry argued that, as the hegemonic power of the liberal system, the United States “can identify its own national interest with the openness and stability of the larger system.” Threats to this system are threats to the United States; sustaining the health of this system is a vital national security interest of the United States. Nau again: “Converging identities safeguard national security just as surely as dominant military power.” Narrowly focusing on the territorial security of the United States while neglecting the nature of world order—is it healthy or anemic? Hostile or friendly? Stable or unstable?—is short-sighted. Liberal order is the outer perimeter of American security.

The current distribution of norms is highly favorable to the United States. It has not always been so. World order has changed and evolved over centuries—but not randomly. The culture of world politics is largely the creation of its most powerful members, which is why realists are right to stress the enduring importance of power in world politics. For the past three hundred years, the most powerful states in the international system have been the United Kingdom, the United States, and, since World War II, the liberal democratic states of Western Europe and Japan. Powerful, illiberal states have launched repeated challenges to liberal ascendancy; all have failed. Scholars and policymakers have called this, variously, the “maritime system,” the “Open Door,” the “democratic community,” and a strategy of “deep engagement” to sustain the “free world,” or “liberal order.”

Politically, liberal order favors liberal democracies, the rule of law, and civil liberties. Economically, liberal order means capitalism, relatively free trade and low trade barriers, freedom of the seas, neutral rights, the sanctity of contract, and peaceful rule-based dispute adjudication. Internationally, liberal order means nonaggression and territorial inviolability—with limited exceptions for humanitarian intervention—and favors intergovernmental cooperation on issues of global concern.

Objections, Costs, and Benefits

Some critics, like scholar Christopher Layne, have criticized this view on the grounds that it leads to overextension. “By definition, any strategy that equates security with the defense of de-territorialized ‘milieu goals’—like openness—rather than with tangible strategic factors—like geography and the distribution of power—is open ended, because it is impossible to fix a point beyond which America’s security interests are not implicated.” This is unpersuasive. It is possible to fix limits (although U.S. policymakers have sometimes failed to do so). The “milieu” is not undefined and featureless, requiring an all-or-nothing defense: it is made of up specific things like the presence or absence of pirates in strategic waterways; the proportion of power possessed by a state expressing a hostile ideology; the efficiency and competence of liberal institutions; and more. Fiji’s autocracy is irrelevant to the survival of liberal order; Pakistan’s is not. The Convention of the Rights of the Child is dispensable; the Nuclear Non-Proliferation Treaty is not. The United States’ efforts to sustain a favorable milieu can and should be strategic and selective, largely by focusing on regions with the greatest concentration of wealth, power, and danger.

A second objection is similar to the first. Fostering liberalism abroad may be possible, but it may not be cost-effective. Do the benefits of upholding liberal order outweigh the costs? Or is the U.S. at risk of “imperial overstretch” and “strategic overextension,” the point at which the resources required to maintain its position exceed the benefit of doing so? Scholars have computed the direct cost of different military deployment patterns and found, unsurprisingly, that the cost of a globally-deployed U.S. military presence is higher than the cost of “restraint”—but, importantly, the cost of either is easily sustainable given the United States’ massive economic foundation.

The direct cost of a globally-deployed military posture—probably between four and six percent of GDP—is nowhere near “imperial overstretch.” Since 1940, the United States spent an average of 7.4 percent of its GDP on defense. Since the end of the Cold War, the average has dropped dramatically to 3.7 percent, is currently 3.3 percent, and is scheduled to drop to 2.7 percent by 2020, according to the Office of Management and Budget. The United States sustained more than twice that level of defense spending for four decades during the Cold War. The greatest barrier to a modestly larger defense posture is political will, not economic sustainability.

The real argument is over the opportunity cost of investing U.S. resources, energy, attention, and prestige in upholding liberal order versus not doing so. Advocates of restraint argue that the United States pays an opportunity cost by investing in military and diplomatic tools rather than domestic economic and social programs, such that it is undermining its own economic health by overextending itself abroad. One problem with this approach is that the economic models that purport to show the economic impact of military spending versus domestic spending are uncertain and contested; some scholars contend that military spending actually contributes to economic growth. Paul Kennedy’s classic argument about the relationship of economic strength to military power was drawn from cases of imperialism and mercantilism; its logic does not apply to the novel case of liberal order-building. The United States rarely conquers and administers territory, so it neither incurs the costs nor takes the direct benefit of imperial rule, limiting the usefulness of analogizing to past great powers. In fact, liberal order is an economic asset to the United States because it includes an open trading regime.

Another problem with the argument about relative opportunity costs is that the United States would pay an enormous opportunity cost by not investing in liberal order, a point advocates of restraint rarely consider. Liberal order already exists and provides benefits to the United States. The opportunity to sustain the already-existing liberal order—by staying in NATO, for example—is a major asset for the United States. Divesting from liberal order forgoes those benefits. And even if policymakers are uncertain about the benefits of liberal order, prudence counsels continued investment. Sustaining an existing liberal order is cheaper than building a new one from scratch; sustaining liberal order at low cost today makes more sense than divesting from it only to rebuild it at high cost later.

The debate is intractable because liberal order has no price tag: Liberal order is either priceless or worthless. Advocates of restraint believe that liberal order has zero value because they do not believe the culture of world order matters for American security. Advocates of internationalism argue that liberal order brings concrete benefits and its absence would incur costs, but not ones that can be quantified. If the culture of world order matters at all, it matters a great deal; policymakers should certainly take great care with the kind of culture they help create. The question is not “how much does liberal order cost?” but rather “what kind of world do we live in?” If the world is as described by advocates of restraint, then no conceivable level of costs associated with upholding liberal order would be justified. But if the world is as described here, then, similarly, no level of benefits associated with restraint are very attractive.

A final objection to this view of American security and world order is that it is unsustainable. Liberal order depends on American power, in this view, and it was only built because of the historically unprecedented disparity of power between the United States and others. As China and other developing countries close the gap between themselves and the developed world, America’s relative power will decline, and the United States’ ability to sustain liberal hegemony will erode. If true, grand strategies that aim at the continuation of liberal order are expensive projects in proving the futility of working against the grain of history.

This objection depends on two premises: that liberal order depends on American hegemony and that American power is inevitably declining. Both are contestable. First, liberal order is much older than American hegemony, having antecedents in the Pax Britannica of the nineteenth century and perhaps earlier. It does not depend on unipolarity or hegemony: The British built their version of liberal order within a multipolar balance-of-power system, and the United States within the bipolar Cold War. Today the rise of China or a belligerent Russia might end American hegemony (and might not), but liberal order could nonetheless live on. The rise of India and the enduring prosperity of liberal democratic Europe and Japan suggest liberal order has many pillars to stand on.

Second, while American relative power has declined if measured in crude material terms such as America’s share of global GDP, that is not a very full measure of the United States’ ability to secure its interests. The United States has arguably increased its ability to achieve its goals by fostering a favorable international environment. Liberal order is an extension of American—and other democracies’—power. By entrenching liberal norms, it gives them a life beyond the fiat of any single liberal state. The system is self-reinforcing: Liberal states uphold liberal order, which in turn enhances their power to defend and extend the system. Whether American unipolarity lasts or not, there is ample reason to believe that American influence and liberal order are sustainable. Unipolarity is a tool or, better yet, an opportunity. The important question is what America should do with its unipolarity while it lasts. Using it to build liberal order enhances American security and extends American influence even if America’s relative material power declines.