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.