On January 7, 1946, 20,000 American servicemen held a mass meeting in Manila, at which they listened to sergeants, corporals, and other veteran GIs demand that the Army ship them home. They were homesick, but many also protested U.S. plans to station troops in North China, Indonesia, and the rest of the Philippines, where Communist insurgencies and nationalist revolts challenged old oppressors. This “Bring the Boys Home” movement quickly spread throughout the Far East and won widespread support back in the United States. Bowing to the popular pressure, the War Department soon accelerated troop demobilization to fill every available ship with veterans who were eager to return home.

The revolt of the overseas servicemen dissipated within weeks, but it encapsulated much of the tension that would govern U.S. diplomacy and politics during the post–World War II years. The United States became the world’s preeminent military and economic power, with millions of troops spread all over the globe. Much of Europe and Asia lay in ruins, while the U.S. industrial machine remained untouched by the ravages of war. But the deployment of American strength—and the purposes for which it would be used—generated unexpected controversy both at home and abroad.

For all their prosperity, Americans did not feel secure in 1946. The planet was dividing into two armed and hostile camps, embodying different social and economic systems: one composed of nations that were allied to or occupied by the Soviet Union, the other a slightly looser network of states led by the United States. This military and ideological rivalry—dubbed the “Cold War” by American financier and presidential adviser Bernard Baruch—generated an expensive and dangerous arms race and bloody conflicts over the next three decades in China, Greece, Korea, Vietnam, and Central America.

America’s protracted struggle with the Soviets gave rise to a dual set of containments: abroad, the U.S. helped erect a worldwide set of anti-Communist alliances; at home, the Cold War generated a sharp turn to the right, containing within well-policed boundaries the ideas and activities that were considered politically acceptable. The unions recruited new members and conducted frequent strikes early in the postwar era, but government regulations forced radical anticapitalist ideas out of the house of labor. “McCarthyism,” which first took its name from the inquisitorial investigations conducted by Wisconsin senator Joseph McCarthy, provided a convenient label for the repressive atmosphere created by the political obsession with the American Communist Party.

Since the 1950s, American politics and society have been transformed in two fundamental ways. First, an amazingly creative mass movement of Black and white citizens swept aside the structures of legal segregation and discrimination that for almost one hundred years had mocked the Union victory in the Civil War. The civil rights revolution gave enormous energy to the reforming impulse that culminated in the 1960s in President Lyndon Johnson’s “Great Society.” Medical care for the poor and elderly, greater access to education, a more liberal and less racist immigration law, and a highly touted “War on Poverty” seemed but a continuation of the New Deal social agenda. The movement for African American liberation made all Americans more rights conscious, raising the expectations and aspirations of young people, women, LGBTQ+ people, Americans with disabilities, Native Americans, and all those who felt marginal to the mainstream of American life. The women’s movement that began late in the 1960s offered a particularly potent political and cultural challenge to the gender inequalities that were so thoroughly embedded within the very structure of marriage, work, and public life.

The rights revolution of the 1960s also transformed working-class America. The typical worker of the 1950s—a male breadwinner in a blue-collar union job supporting a family—had virtually ceased to exist. The massive entry of women into the paid labor force has radically altered the character of American family life. Moreover, since 1965, a wave of immigrants from Asia, Latin America, and Eastern Europe has made the working class of most cities even more cosmopolitan than it had been in the years of trans-Atlantic immigration before World War I.

But these great social and ideological changes shifted American politics to the right, not the left. Indeed, the second signpost to the history of the last half century has been the unexpected rise of a powerful conservative current in American politics. Liberalism had but a brief flowering in the 1960s because the polarization generated by the war in Vietnam, the revival of feminism, and the upheaval in race relations fractured the coalition that had long sustained the majority status of the Democratic Party. Then, just a decade later, the unexpected stagnation in U.S. living standards brought into question the even older New Deal linkage between economic prosperity and activist government. In the 1970s and early 1980s, a sharp decline in the productivity and profitability of American business ended the great postwar boom that had doubled Americans’ living standards in just a generation. As high-paying industrial jobs vanished and the unions shrank in size, white working-class loyalty to the Democrats declined as well.

The collapse of liberalism in the 1970s helped to pave the way for the presidency of a conservative Republican, Ronald Reagan, whose successful efforts to roll back taxes, cut social spending, curb union power, and expand the military represented a decisive postwar break with the political legacy of the New Deal. The influence of Reaganite Republicanism proved as great as that of any twentieth-century president. The Democratic Party itself became much more conservative. And even with the end of the Cold War and the improved economy under the two-term presidency of Democrat Bill Clinton, efforts to expand the welfare state and legitimize a socially activist government proved largely unsuccessful.

At the beginning of the twenty-first century, issues of international security, increasing economic inequality, and cultural divisions defined the election and presidency of George W. Bush. The terrorist attacks on September 11, 2001, generated a wave of patriotic nationalism that the Bush Administration leveraged to declare a virtually unlimited “war on terror.” In addition to a military invasion of Afghanistan, which destroyed much of the al-Qaeda infrastructure there, President Bush inaugurated a far-reaching expansion of the federal government’s authority to investigate and detain suspected terrorists, both at home and abroad. In the spring of 2003, the Bush administration launched an unprovoked invasion of Iraq that easily toppled dictator Saddam Hussein but then led to a protracted and increasingly unpopular war against a well-armed and highly motivated insurgency.