Since the Second World War, the external order of American power has been largely insulated from the internal political system. If party competition in the domestic arena has rested on rival electoral blocs, combining significant fluidity of contours with increasing sharpness of conflicts, in the global arena such differences are far less. Commonality of outlook and continuity of objectives set the administration of empire apart from rule of the homeland. footnote1 In some degree, the contrast between the two is a function of the general distance between the horizons of chancelleries or corporations and of citizens in all capitalist democracies—what happens overseas is of much greater consequence to bankers and diplomats, officers and industrialists, than to voters, issuing in correspondingly more focused and coherent outcomes.

In the American case it also follows from two further local particulars: the provincialism of an electorate with minimal knowledge of the outside world, and a political system that—in strident contradiction with the design of the Founders—has increasingly given virtually untrammelled power to the executive in the conduct of foreign affairs, freeing presidencies, often baulked of domestic goals by fractious legislatures, to act without comparable cross-cutting pressures abroad. In the sphere created by these objective conditions of policy-formation, there developed from mid-century around the Presidency a narrow foreign-policy elite, and a distinctive ideological vocabulary with no counterpart in internal politics: conceptions of the ‘grand strategy’ to be pursued by the American state in its dealings with the world. footnote2 The parameters of these were laid down as victory came into sight during the Second World War, and with it the prospect of planetary power.

The us imperium that came into being after 1945 had a long pre-history. In North America, uniquely, the originating coordinates of empire were coeval with the nation. These lay in the combination of a settler economy free of any of the feudal residues or impediments of the Old World, and a continental territory protected by two oceans: producing the purest form of nascent capitalism, in the largest nation-state, anywhere on earth. That remained the enduring material matrix of the country’s ascent in the century after independence. To the objective privileges of an economy and geography without parallel were added two potent subjective legacies, of culture and politics: the idea—derived from initial Puritan settlement—of a nation enjoying divine favour, imbued with a sacred calling; and the belief—derived from the War of Independence—that a republic endowed with a constitution of liberty for all times had arisen in the New World. Out of these four ingredients emerged, very early, the ideological repertoire of an American nationalism that afforded seamless passage to an American imperialism, characterized by a complexio oppositorum of exceptionalism and universalism. The United States was unique among nations, yet at the same time a lode-star for the world: an order at once historically unexampled and ultimately compelling example to all.

These were the convictions of the Founders. The radiance of the nation would in the first instance be territorial, within the Western Hemisphere. As Jefferson put it to Monroe in 1801: ‘However our present interests may restrain us within our limits, it is impossible not to look forward to distant times, when our multiplication will expand it beyond those limits, and cover the whole northern, if not the southern continent, with people speaking the same language, governed in similar forms, and by similar laws’. But in the last instance, that radiance would be more than territorial: it would be moral and political. In Adams’s words to Jefferson in 1813: ‘Our pure, virtuous, public spirited, federative republic will last forever, govern the globe and introduce the perfection of man’.footnote3 Towards mid-century, the two registers fused into the famous slogan of an associate of Jackson: ‘the right of our manifest destiny to overspread and possess the whole continent that providence has given us for the great experiment of liberty and federated self-government’. For a land ‘vigorous and fresh from the hand of God’ had a ‘blessed mission to the nations of the world’. Who could doubt ‘the far-reaching, the boundless future will be the era of American greatness’? footnote4 The annexation of half the surface of Mexico followed in short order.

Once the current boundaries of the United States were largely reached, the same sense of the future took more commercial than territorial form, looking west rather than south. Lincoln’s Secretary of State exhorted his compatriots: ‘You are already the great continental power of America. But does that content you? I trust it does not. You want the commerce of the world. This must be looked for on the Pacific. The nation that draws most from the earth and fabricates most, and sells the most to foreign nations, must be and will be the great power of the earth.’footnote5 What Manifest Destiny and the conquest of Mexico were on land, Commodore Perry and the Open Door could be on sea—the horizon of an American marine and mercantile primacy in the Orient, bearing free trade and Christianity to its shores. With the outbreak of the Spanish–American War, classical inter-imperialist conflict brought colonies in the Pacific and the Caribbean, and full-fledged entrance into the ranks of the great powers. Under the first Roosevelt, Panama was carved out of Colombia as a us dependency to link the two seas, and race—Anglo-Saxon breeding and solidarity—added to religion, democracy and trade in the rhetoric of the nation’s calling.

This was never uncontested. At each stage, eloquent American voices had denounced the megalomania of Manifest Destiny, the plunder of Mexico, the seizure of Hawaii, the slaughter in the Philippines, attacking every kind of racism and imperialism as a betrayal of the anti-colonial birthright of the republic. Rejection of foreign adventures—annexations or interventions—was not a break with national values, but always a possible version of them. From the beginning, exceptionalism and universalism formed a potentially unstable compound. Conviction of the first allowed for belief that the United States could preserve its unique virtues only by remaining a society apart from a fallen world. Commitment to the second authorized a messianic activism by the United States to redeem that world. Between these two poles—‘separation’ and ‘regenerative intervention’, as Anders Stephanson has described them—public opinion could more than once abruptly shift.footnote6

As the us entered the new century, however, such mood-swings were of less significance than the sheer economic and demographic growth of the country. By 1910, American capitalism was already in a league of its own, with an industrial magnitude larger than that of Germany and Britain combined. In an age permeated with social-darwinist beliefs in the survival of the fittest, such indices of production could only mean, for ambitious contemporaries, the coming of a power commensurate with them. As the Civil War felled half a million of his countrymen, Whitman exulted that ‘we have undoubtedly in the United States the greatest military power in the world’.footnote7 Yet after Reconstruction, the peace-time strength of the army remained modest by international standards. The navy—marines dispatched for regular interventions in the Caribbean and Central America—had more future. Symptomatically, the entrance of the United States into the intellectual arena of Weltpolitik came with the impact of Mahan’s Influence of Sea Power upon History, closely studied in Berlin, London, Paris and Tokyo, and a touchstone for both Roosevelts, which argued that ‘everything that moves on water’—as opposed to land—possessed ‘the prerogative of offensive defence’.footnote8 A decade later, Brooks Adams laid out the global logic of us industrial preeminence in America’s Economic Supremacy. In 1900, he wrote, ‘For the first time in human experience a single nation this year leads in the production of the precious metals, copper, iron and coal; and this year also, for the first time, the world has done its banking to the west and not to the east of the Atlantic.’ In the struggle for life among nations, empire was ‘the most dazzling prize for which any people can contend’. Provided the American state acquired the necessary organizational form, the us could in future surpass the imperial wealth and power of England and Rome.footnote9 But when war broke out in 1914, there was still a wide gap between such premonitions and any consensus that America should involve itself in the quarrels of Europe.