Our greatest statesmen understand this connection. In particular, Alfred Thayer Mahan understood it. A naval officer and strategist whose 1890 book, The Influence of Sea Power upon History: 1660–1783, was a theoretical treatise as well as a history that argued for American national greatness through control of the seas, Mahan was in his time a strong influence on politicians such as Theodore Roosevelt and on a generation of foreign-policy theorists. Yet today, outside of a small circle of naval officers—including Chinese officers who admire his idea that under the right circumstances sea power is the key to national greatness—Mahan and his contribution to the American century has been largely forgotten. Notwithstanding, more than ninety percent of the world's trade is conducted by water, and the world's waterways are and will remain the most efficient means for transporting goods.

The two-thirds of a century since the end of World War II have encouraged us to take for granted that the oceans are safe for navigation. The US Navy has created a status quo that we now believe is natural, and we take for granted the origins of this liberal regime on the water. Should a competitor state arise to challenge America's influence on the oceans, the world's waterways are not likely to remain as friendly to liberal commerce as they have been since 1945. And the consequences to the American economy would be incalculable—as they were to the Dutch when they vanished as an international force in the late eighteenth century due to the loss of dominant sea power.

As Mahan wrote, naval power often proves "more silent than the clash of arms"—as influential as it is quiet. Yet the influence of sea power on commerce and national security is almost always pushed aside each time a nation feels domestic financial pressures. One reason this happens is that it is difficult to quantify sea power's strategic gains, despite its silent and oft overlooked aim of creating the conditions for stable commercial relations on the world's waterways. Contemporary economic methodology takes for granted the causes that make possible the operation of rational economic laws.

Furthermore, Mahan viewed sea power as the protector of democratic freedom. He saw three things: that Americans have a talent for creating wealth, that sea power is needed to increase that wealth by overseas trade, and that sea power assists in insinuating (on allies and enemies alike) political orders friendly to rational commerce. Like Alexander Hamilton, Mahan saw that expanding wealth would move the international system toward a commercial competition in which the US was likely to eventually gain and hold the upper hand. An additional benefit of successful commercial competition is being able to afford the most advanced military equipment, a strategy the US has continued to pursue. More than assuring the continuation of liberal commerce on the seas and securing freedom from domination by other states, sea power multiplies national power not through competition but through the soft political leverage attained through commercial development.

Nearly four years ago, the US Navy included among its important objectives humanitarian aid and disaster relief, traditional naval activities that are now receiving more attention as a core mission. More than twelve thousand sailors at a time served in support missions on the ground in Iraq and Afghanistan during the height of those conflicts. But serious reductions in the fleet's combat ability as a result of budget cuts now threaten these missions and the overall long-term strategic value of the US military. Needs that look pressing at this or that moment can slowly replace strategy.

Mahan articulated a widely neglected subject in the debate on military strategy: sea power's special significance during times of peace. In his view, the virtue of a mobile maritime force was that it can be deployed and stationed anywhere, nearly at any time, and that its desired effect is primarily indirect and perceptible only over time.

Diverting the economic and military efforts of other states—often persuading competitors or less powerful neighbors to develop in ways guided by our own strategic interests—is most cheaply and effectively achieved by sea power. Attempting the same broad effect with ground forces is rarely practicable or desirable because it leads to charges of imperialism and possible confrontation and tends to provoke costly (to both sides) resistance. Thus, more than any other military branch, the navy, during times of peace, serves as a preventative force that may reassure friends of support, help us gain friends, and dissuade states without navies from bothering to develop them.

Similarly, by clearing the sea-lanes of hostile navies, and protecting the waters with a friendly one, a good navy encourages allies to develop commercially by providing them the routes to enter into commercial markets. Both sides thus benefit, though sometimes disproportionately. For example, how many of the Four Asian Tigers—Hong Kong, Singapore, South Korea, and Taiwan—would have become as wealthy as they did if they had been overshadowed by a hegemonic and threatening naval power?

Mahan foresaw that naval strategy during peace is primarily guided by the following principles. First, rather than allowing competitors to develop their own merchant shipping fleet to support their foreign trade, a great nation preempts them by the projection of sea power. Mahan argues further that a thriving commercial shipping industry is the force that naturally produces a healthy navy, not a force—like that of Kaiser Wilhelm or the Soviet Navy—that exists by whim of a monarch or the command of an autocratic regime. This insight was not implemented by the US in its maritime policies toward China, which over the past decade has acquired several of the largest shipping companies in the world. The US bet on China during Washington's struggle with Moscow, and those who placed this bet—Henry Kissinger foremost among them—have not since reconsidered whether by seeking to offset one danger they helped to create another.

Secondly, Mahan contends that at certain times it may even be a good idea for a state to encourage its competitors to build a blue-water navy independent of a commercial fleet. Such a navy will likely have the appearance of strength, but will be short-lived and financially precarious—but all the more so if the rival simultaneously seeks to dominate on land and at sea. Looking back at the French-Dutch conflict of the seventeenth century for an example, Mahan argues that "the policy of France was constantly diverted, sometimes wisely and sometimes most foolishly, from the sea to projects of continental extension. These military efforts expended wealth: whereas a wise and consistent use of her geographical position [near the sea] would have added to it." If Mahan were alive today, he would note that, given its geographic deadlock with India to the southwest and Russia to the north, China will most likely pursue the way of the sea.

The more subtle strategy, the one best undertaken in peace, is to secure, slowly and almost imperceptibly, territories useful for commerce, territorial management, or as preparation for the possibility of determined commercial competition or armed conflict itself. As a theorist, Mahan would have nodded approvingly at China's efforts to develop the naval facilities and supporting bases in the Indo-Pacific region called the "string of pearls." He observes that, "in peace [naval strategy]?.?.?.?may gain its most decisive victories by occupying in a country, either by purchase or treaty, excellent positions which would perhaps hardly be got by war." Peace for Mahan is a breather, a time when architects of foreign policy look to the direct and indirect effects of far-flung sea power in a future when gun ports are once again opened.

Thus, without spending a lot of money on stationing garrisons abroad or maintaining military bases, a navy becomes an armed chess set whose global maneuverability equals its adaptability to use force, threaten to do so, or assist states in need. Moreover, restricting or limiting a strategic rival's access to global waters also indirectly controls their military development by forcing a choice between developing on the sea or on land. A contemporary example might be that of the Russian Federation. Even with a windfall from its oil and natural gas income, Russia cannot yet afford a competitive blue-water fleet. The United States' global naval power pressures Russia to maintain its continental forces, to invest in sustaining ground troops, arms, and equipment. Russia's strategic attention is directed toward energy monopoly and Central Asian territory rather than into US-dominated waters. The Russians are not competitors to the US on the sea because of American transoceanic sea power and Russia's own internal limitations.

Liberal commerce orders relations between states through the principle of interest. But Mahan questions whether international commerce is possible without the support of global sea power, or whether, in the absence of such power, only variations of disorder, war, and piracy—or domination by a great despotic power—persist on the seas. For Mahan, a good navy is the force that establishes the grounds for liberal trade on the sea and safeguards its continuation.

If states relate to one another through either alliance or competition, as Mahan believes they do, successful commercial states follow one of three tracks: they seek to turn other states into allies by guiding them toward democratic laws through commercial pressure or military influence, as the US did in Japan and Korea; or to control the world's waterways for the purpose of "managing" trade; or to send out colonies.

Manufacturing economies, as Mahan argues, rely on naval power to protect commerce. Service economies—such as the US is becoming—may at first glance appear to rely less and less on sea power as the need to protect the ocean-borne import and export of raw materials and finished goods decreases. But service economies in fact depend even more on sea power because of the absence of a shipping fleet, and the inevitable arrival of foreign ones.

A large merchant fleet hasn't existed in the US since before the Civil War. But even for a nation that has replaced a manufacturing with a service economy and rented foreign hulls to carry its own goods—as the US has—the ability to hold strategic choke points, along with other advantages of sea power, such as the ability to project power and command the seas, remains critical to the order on which freedom of navigation depends. The sea routes whose safety such states have become accustomed to are at risk from new forms of rule based on new interests and different ideas of international order. When the Royal Navy abandoned its forward presence in the Western Pacific to Japan in 1904, a new order established itself there.

The multidimensional character of Mahan's insights about sea power and the way it mirrors a changing international order helps explain the popularity he has enjoyed in China. The country's rapidly enlarging merchant fleet and developing manufacturing economy are linked to a rising naval fleet. Mahan would have seen at once that if, at the same time that the Chinese are focusing on maritime issues, the US combat fleet's prospects for long-term health are fading, international conflicts between the two powers will increase. Without dominant sea power, what are the choices? Land intervention—the costliest and most politically unpopular option—or a gradual decline into impotence. By cutting its naval budget, the US loses strategically, as well as commercially. And, again, our economists do not and cannot calculate the monetary losses of losing entire markets and the consequences of entering into antagonistic economic relations where competitors, not the market, set prices. The replacement of English with American naval power meant little since England and the US shared similar views of international order. The replacement of America's dominant position as a global sea power by, for example, China, would have much more serious consequences—not just for us, but for our Asian and European allies who depend on the liberal order we have established.

Preserving command of the seas supports the United States' competitive advantage. It allows communication with the alliances that we hope to preserve. And it gives the US strategic options. If the debt crisis the US is trying to address is resolved at the expense of command of the seas, the cure to our financial woes will prove a Pyrrhic victory.

The world's waterways are of themselves neutral and without a preference for the state that governs them. Different states bring their own order of governing the seas, and the US brings with it liberal economics. It is difficult to imagine serious discussions of international maritime law, or treaties that establish a law of the seas, had the Soviet Union emerged victorious in the Cold War.

America's allies in the Pacific are currently being pressed more immediately by the Chinese than we are. They see, as Americans tend not to, that the US is in a long-term competition with China, and recognize, as we don't, that the Chinese desire slowly to push US sea power out of the international waters close to them. The only force standing in the way of such a transition, which would destroy a complex web of alliances for the US in the Pacific, is our current sea power.

Alfred Thayer Mahan offers the intellectual arguments that address what the US stands to lose economically and militarily—and all that China will gain—if there is a profound shift of power in the Western Pacific. Commerce, he believes, plays to the natural advantage of an enterprising people who are largely free to act upon their judgment and enterprising spirit. But commercial advantage and our enterprising spirit relies equally on the ability to keep open the oceanic arteries through which commerce must be able to flow. This equation is set on its head when prosperity becomes an important instrument to justify single-party rule—as in China, where freedoms of commerce are restricted by the state's pressing requirement, for example, to employ millions; by an understanding of commercial freedom that is wholly separate from political freedom; and by a parallel view of sea power that sees the interruption of commerce as a personal threat to those who rule the state.

Mahan saw correctly that American greatness depends on dominant sea power. He understood the close connection between domestic prosperity and maritime preeminence. The acceptance of his ideas at the beginning of the twentieth century helped immeasurably in encouraging both, the condition of which is the only one in the memory of Americans alive today. But perpetual permanence is indeed the illusion of every age, as the possibility of a much diminished US Navy raised by ongoing budget negotiations should be a reminder.