Even more than I realized when I began this book, foreign policy has been central to the national experience. External assistance was essential to the birth of an independent United States; concerns about international commerce and foreign threats decisively influenced the form of government created in the Constitution of 1787. Foreign policy was instrumental in securing the young republic's political experiment, establishing a continental Union, and determining the outcome of its Civil War. During the nation's second full century and beyond, foreign policy has become even more critical to its prosperity and security.

Throughout its history, the United States has taken a distinctive approach toward foreign policy. Americans have held decidedly mixed views about their place in the international order. On the one hand, they have been allured by the riches of the world, and from the Revolution to the present, the pursuit of economic self-interest has produced a high level of global involvement. On the other, from the outset they expressed disdain for traditional European power politics and viewed themselves as a people apart, the harbingers of a new world order.

From Puritan leader John Winthrop's proclamation of a "city upon a hill" through George W. Bush's born-again zeal, Americans have seen themselves as a chosen people with a providential mission. This ideal has spurred a drive to do good in the world, manifested in the work of merchants, missionaries, and educators. It undergirded the Wilsonian dream of the United States as world leader and a world reformed according to American ideals.

This ideal has also spawned a certain arrogance in America's dealings with other peoples that was used to justify the expulsion of Native Americans, the wresting from Mexico of one-third of its territory, and the imposition of colonial rule on Filipinos and Puerto Ricans. From an ill-fated incursion into Canada in 1775 to the 2003 invasion of Iraq, America's sense of its grand historical mission has been used to rationalize the extension of liberty by force. Certain of their righteousness, Americans confidently expected to be welcomed as liberators. The ironic result, in most cases, has been to spark nationalist opposition among the people invaded.

America's democratic system has also given a distinctive hue to its foreign policy. From the beginnings, foreign policy has been the object of fierce partisan dispute. On occasion, an aroused public has pushed the government to act. More often, public indifference or apathy have brought about increasingly sophisticated efforts on the part of leaders to inform, "educate," and manipulate public opinion. The division of powers between executive and legislative branches has added another area of confusion and conflict. The nation's peculiar approach to foreign policy has long bemused and befuddled foreign observers, producing sometimes ingenious efforts to influence the U.S. political process.

Despite its claims to moral superiority and disdain for Old World practices, the United States throughout its history has behaved more like a traditional great power than Americans have realized or cared to admit. U.S. political leaders have energetically pursued and zealously protected interests deemed vital. In terms of commerce and territory, they have been aggressively and relentlessly expansionist. From Louisiana to the Florida, Texas, California, and eventually Hawaii, they fashioned the process of infiltration and subversion into a finely tuned instrument of empire, using the presence of restless American settlers in nominally foreign lands to establish claims and gain additional territory. During the Cold War, when the nation's survival seemed threatened, they scrapped traditional notions of fair play, intervening in the affairs of other nations, overthrowing governments, even plotting the assassination of foreign leaders.

Popular notions to the contrary, the United States has been spectacularly successful in its foreign policy. In the space of a little over 200 years, it conquered a continent, established dominance over the Caribbean and Pacific Ocean areas, helped win two World Wars, prevailed in a half-century Cold War, and extended its economic influence, military might, popular culture, and "soft power" throughout much of the world. By the beginning of the 21st century, it had attained that "strength of a Giant" Washington had dreamed of.

Ironically, as the nation grew more powerful, the limits to its power became more palpable, a harsh reality for which Americans were not prepared by history. The nation's unprecedented success spawned the notion that it could do anything it set its mind to. Success came to be taken for granted. Despite its vast wealth and military power, the United States had to settle for a stalemate in the Korean War. It could not work its will in Vietnam or Iraq, nations whose complex societies and idiosyncratic histories defied its efforts to reshape them, causing frustration and disillusionment at home.

The emergence of a new 21st century threat in the form of international terrorism and the devastating September 11, 2001 attacks on New York's World Trade Center and the Pentagon underscored another hard reality: power does not guarantee security. On the contrary, the greater a nation's global influence, the greater its capacity to provoke envy and anger; the more overseas interests it has, the more targets it presents to foes and the more it has to lose. America's unparalleled power could not assure the freedom from fear its founders had dreamed of. Post-9/11 difficulties in Iraq and Afghanistan underscored a fundamental "lesson" of geopolitics, that power, no matter how great, has limits. America's unipolar moment turned out to be fleeting. By the end of the first decade of the new century, experts were again speaking of a nation in decline.
    -INTRODUCTION: From Colony to Superpower: U.S. Foreign Relations since 1776 (Oxford History of the United States) (George C. Herring)