Successful statecraft aligns interests with circumstance. In the immediate aftermath of World War II, a generation of statesmen grasping this essential truth presided over a radical reorientation of basic U.S policy. The result was a half-century of American global primacy.

Now, however, the era of American primacy has ended. The imperative of the present moment is to adjust U.S. policy to rapidly changing circumstances. In the two decades since 9/11, members of the foreign policy establishment have sought to finesse or avoid this issue. The failure of America’s 20-year war in Afghanistan suggests that this is no longer possible.

Proponents of American primacy commonly rely on euphemisms to describe it, with “American global leadership” a particular favorite. Critics with an aversion to euphemism prefer terms such as “hegemony” or “imperialism.” The correct term is “privilege.”

Writing in 1948, George Kennan, director of the State Department’s Policy Planning Staff, made an essential point. “We have about 50 percent of the world’s wealth, but only 6.3 percent of its population,” he wrote. “Our real task in the coming period is to devise a pattern of relationships which will permit us to maintain this position of disparity.”

With this purpose in mind, Kennan’s associates, chief among them George Marshall, Dean Acheson, James Forrestal and Paul Nitze — White males all — undertook a series of initiatives aimed at perpetuating this position of disparity. Their approach centered on devising mechanisms to project American power globally.

Among their best-known initiatives were the Truman Doctrine, the Marshall Plan and NATO. Hardly less important was the National Security Act of 1947, which, among other things, created the CIA; NSC-68, a secret document that in 1950 committed the United States to the pursuit of permanent military superiority; and the fashioning of Strategic Air Command into an instrument of genocidal nuclear attack.

Not everything worked out as planned. Considerable miscalculation and folly ensued. Examples include a frenzied arms race; the emergence of a corrupting military-industrial complex; a brush with Armageddon during the Cuban missile crisis; and a war gone horribly wrong in Vietnam.

But on balance, throughout the decades-long Cold War, Americans enjoyed a way of life that made the United States the envy of the world — free, democratic and prosperous. So at least most Americans themselves firmly believed.

The end of the Cold War served to affirm such convictions. Hence, the collapse of the Soviet Union and the demise of communism prompted few second thoughts regarding the now well-entrenched power projection paradigm. Nor did 9/11. Indeed, in response to the terrorist attack on New York and Washington, George W. Bush doubled down, describing the nation’s new enemy as “heirs of all the murderous ideologies” of the prior century. The United States would deal with them precisely as it had dealt with “fascism, Nazism and totalitarianism.” The recent past would define America’s future.

So at Bush’s behest, the nation embarked upon a Global War on Terrorism that targeted an “Axis of Evil” consisting of three nations uninvolved in 9/11. Unlike Iraq, Iran and North Korea, Afghanistan had actually figured in the terrorist attack. In practice, however, in the ensuing global war, Afghanistan figured as no more than an afterthought. Washington’s priorities lay elsewhere.

By this time, the correlation between U.S. policy and Kennan’s position of disparity had long since begun to unravel. By 2000, the United States accounted for 32.6 percent of the world’s wealth. A mere two decades later, America’s share of global wealth had shrunk to less than 30 percent. Simultaneously, within the United States itself, the gap between the rich and the non-rich was increasing by leaps and bounds, contributing to profound domestic unrest.

“Free, democratic and prosperous” no longer suffices to describe contemporary America, even in the eyes of many Americans. The postwar formula for sustaining a position of global privilege is no longer working. Indeed, it has become irrelevant at best or counterproductive at worst.

Ever the realist, George Kennan would have unhesitatingly acknowledged that fact. For that reason, he would certainly have supported President Biden’s decision to end the war in Afghanistan.

But as a strategist, Kennan would have gone further, recognizing that the most pressing threats to American security and well-being are no longer “out there” in Central Asia or in other distant theaters but “back here.” Those threats include disease, climate chaos, environmental deterioration, porous borders, the erosion of personal privacy and, perhaps most insidiously, the unraveling of domestic comity.

The paradigm of power projection, with its emphasis on military intervention abroad, no longer provides a relevant response to these threats.

The genius of Kennan and his contemporaries was to recognize the imperative of fundamentally changing America’s approach to the world. The lesson of Afghanistan, confirmed by the astonishing display of incompetence that has accompanied the U.S. withdrawal, is that it’s past time for the present generation to do the same.

The American war in Afghanistan ends in bitter humiliation. But it should also serve as a wake-up call. The age of American privilege is gone for good.

The most pressing task in the coming period is to devise a pattern of relationships that will refurbish and renew the prevailing conception of American freedom. That task begins with providing for the safety and well-being of Americans where they live.