American national security policy in the 21st century is conducted on the foundations of a global network of military bases and strategic alliances that first emerged during World War II and the early years of the Cold War. The American security network had many fathers, above all Franklin Roosevelt and Harry Truman. One important intellectual contributor, however, is barely known today: Nicholas John Spykman, a Dutch-American geographer who was the Sterling Professor of International Relations at Yale. In the late 1930s Spykman published several articles in the American Political Science Reviewthat considered the relationship between geography and politics. He later wrote two books that bore upon U.S. war and post-war strategy: America’s Strategy in World Politics: The United States and the Balance of Power (1942); and The Geography of the Peace (1944), which was published a year after Spykman’s death. (America’s Strategy has recently been republished, with an introduction by Francis P. Sempa.)

Spykman was a balance of power realist who argued that American security depended to a first order on preventing a hostile power or coalition of powers from dominating the Old World. The resources of the “World Island” of Eurasia, if combined under a hostile power, could simply overwhelm those of the Americas. The ocean would become a highway, not a barrier, to foreign invasion or, more likely, to economic strangulation, and political intimidation and subversion. This balance of power logic—controversial then as now—was hardly original. But Spykman provided a conceptual map that proved highly congenial to key civilians and military officers in the emerging U.S. national security establishment.

Spykman’s precise influence on policy is difficult to document but his major ideas resonated with those strategists who wanted to move the United States permanently beyond hemispheric-oceanic isolationism, while avoiding the mistakes of Woodrow Wilson. Wilson, they thought, had pursued an overly ambitious agenda during and after World War I, one that made no distinction between vital and peripheral U.S. interests and that turned democratization and self-determination into categorical imperatives. Wilson’s intransigent approach to the Versailles Treaty and the League of Nations divided what was otherwise a political majority of conservative and liberal internationalists, who agreed on the need for the United States to “look outward” and participate actively in the security affairs of Eurasia.

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The catastrophic experience of the 1930s and early 1940s, which put Western civilization at such grave risk, convinced internationalists of all stripes of the need to develop a politically persuasive post-war grand strategy—one that grounded idealistic American involvement in Eurasian affairs in specific and definable material interests. Spykman provided an easily understood geopolitical template that defined and prioritized those interests. (In doing so, Spykman drew upon, but modified significantly, the concepts of the British geographer Halford Mackinder.) First, Spykman concluded that America was best defended—indeed, it could only be defended—forward, in Eurasia. This required strategic alliances and overseas bases. Second, he argued that a properly-structured forward defense in Eurasia was militarily feasible despite changes in technology (airpower and railroad transportation) that seemed to advantage large continental states over maritime powers. Third, a close reading of Spykman indicated that American strategic interests outside the Americas were not indiscriminate or open-ended. Spykman’s analysis offered a middle ground between those who sought to fall back on a defensive hemispheric security system, and those who believed that overseas threats were so grave that preventive war and American global hegemony—or world government—were the only alternatives to totalitarian domination of Eurasia.

According to Spykman, America’s principal security concerns were located in the “Rimland” of Eurasia. The Rimland, broadly speaking, included Western Europe, the Maghreb, the Middle East, and continental South, Southeast, and East Asia. This region contained the majority of the world’s population and natural resources. The Rimland was connected by a series of marginal seas, such as the Mediterranean. The gravest threat to the global balance of power would occur if a single power or coalition of powers dominated the Rimland. That power could then close off communication between what Mackinder had called the Heartland—essentially Russia and Eastern Europe—and the offshore islands and continents, above all, the United States. By isolating the offshore powers from Eurasia, the united Rimland power bloc would be able to dominate the Heartland, organize the World Island’s resources, and present a very real possibility of global hegemony. Recent contenders for world domination had largely come from within the Rimland itself (Austria, Spain, France, and Germany), but the threatening power could also come from the offshore islands (e.g., Japan) or the Heartland (Russia).

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Spykman’s key proposition was that American security depended on ensuring that the states of the Rimland remained independent from a would-be hegemon. Modern technology and communications were such that threats to the Rimland could emerge very rapidly. The United States could no longer afford to hang back and see how events developed overseas, but must instead become actively engaged across the oceans during peacetime, through alliances and military bases that maintained air and maritime access to the Rimland and that preserved the security of the marginal seas. The United States need not be responsible entirely for the security of the Rimland because other powers would naturally align with it against any hegemonic threat, irrespective of their political orientation.

Spykman, writing in 1942-43, assumed that the natural post-World War II security alignment would be that of Britain (with its global empire along the Rimland), the Soviet Union, and the United States, all of which shared the desire to suppress the revival of a German or Japanese threat to the balance of power. Spykman did not dismiss the possibility of a Soviet drive for hegemony, but he concluded that the Heartland lacked the resources and the easy invasion routes that would allow it to dominate the Rimland against the counter-alliances which the United States could form. He believed that Soviet leaders could be made to appreciate the limits of their power, as long as they were convinced that the United States would remain actively involved in Eurasian security.

When Soviet behavior in the late 1940s indicated that Stalin had not grasped this essential geopolitical point, American officials, consciously or not, applied the logic of Spykman’s conclusions against Moscow when developing the national security policy known as containment. The United States could not withdraw from Eurasia because the war-weakened Rimland was unable to resist unaided a Soviet drive for global hegemony. But the states of the Rimland, especially once they recovered from the war, contained ample resources to defend themselves, with the aid of the United States. Spykman’s strategy required a much larger commitment of peacetime resources and overseas involvement than Americans were accustomed to, but they were not so massive as to bankrupt the country or force it to abandon its constitutional order. The power-political challenge of creating an anti-Soviet dike seemed manageable because of the strategic contribution and positional advantages supplied by the Rimland states. The Soviet challenge was not so overwhelming as to require the adoption of a constant near-war state of readiness or the resort to preventive war to forestall an otherwise inevitable defeat.

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The devil, of course, was in the details, to which Spykman could not offer authoritative guidance. Should containment be thought of in terms of a series of strong points or a continuous line? To what degree should containment be thought of in military-strategic terms, as opposed to its political, economic, or cultural dimensions? Did the development of nuclear weapons, unforeseen by Spykman, strengthen or compromise the defense of the Rimland? Would forces outside the scope of strict geopolitical analysis—above all, ideology and nationalism—trump or reinforce the logic of containment? Would Americans or other peoples become too weary, bored, or frightened to wage the long twilight struggle? Should American policy be limited and reactive—designed merely to see that the Rimland remained divided—or should it proactively seek to unite the Rimland (and the heavens above?) to compel an end to the Soviet hegemonic threat? Could the Soviets achieve such a degree of success in breaching the dike of containment, or in developing a first-strike threat, such that the United States must adopt a near-war state of readiness or even preventive war? The varying answers to these questions contain in themselves the history of the Cold War. They are not without interest in present times.