Kennan’s insight was that a long-term, complex struggle wasn’t best judged in terms of winning or losing. Communism wasn’t something we could immediately conquer. The same holds true for Al Qaeda, a movement that, like Soviet communism, offers its subjects oppression and poverty. Time is on our side — particularly if we act in a way that doesn’t inflame our enemies’ pride and anger and win them new recruits.

Kennan’s insistence on a political strategy, rather than a military one, makes more sense now than it did when he published his essay. Applied today, that advice would entail spending more time and money building up our Muslim allies. The Center for Strategic and International Studies reports that only about $900 million of the $10 billion we’ve given Pakistan since 2002 has gone to health, education and democracy promotion. Most of the rest has gone to the military. The Bush administration has recently taken steps to change this ratio. But Kennan, one of the authors of the Marshall Plan, would have wanted the numbers to be closer to the reverse.

A 21st-century rendering of X’s vision of containment would involve the closing of the Guantánamo Bay detention camp, an unambiguous renunciation of torture and an abandonment of the notion that our legal and moral norms don’t apply to the current struggle. Kennan believed we gave our opponents a propaganda victory each time we acted in a manner unfitting of our ideals.

“To avoid destruction,” Kennan concluded the X article, “the United States need only measure up to its own best traditions and prove itself worthy of preservation as a great nation.”

We can’t know for sure how his recommended, wholly political version of containment would have fared in the cold war. But we do know that a militant foreign policy didn’t lead to nuclear war and did, eventually, help bring about the collapse of Soviet communism. We also know that a strong offensive policy has yet to succeed against Al Qaeda.

Kennan died two years ago at the age of 101. One of his last public statements was a critique, in 2002, of the looming Iraq invasion. War, he said, was too unpredictable, and this one wasn’t worth it. As he wrote to Lippmann six decades ago, “Let us find health and vigor and hope, and the diseased portion of the earth will fall behind of its own doing. For that we need no aggressive strategic plans, no provocation of military hostilities, no showdowns.”