The United States is in the midst of the second great immigration in its history. In the course of the 1980s, between 8 and 9 million immigrants are expected to enter the United States, whether legally or illegally, a number about 50 percent larger than that of the 1970s and far greater than that of any decade since World War I. This chapter explores the assumption that there is a significant relationship between the nation's ethnic composition, the consequence of immigration, and the general principles of the nation's foreign policy. The postwar circumstances thereby illuminated something of significance that had long been at least partially obscured by the US outlook and policy of isolation from Europe's politics and wars. The fact that the United States was almost entirely made up of European peoples continued to influence the nation's foreign policy in the postwar period.