“And the war will end by the end of next year . . .

In the elusive search for an Obama Doctrine, that struck me as a telling phrase when I heard the president deliver it last week as he and British Prime Minister David Cameron took a couple of questions from reporters.

Obama was speaking about the withdrawal of U.S. and allied combat troops from Afghanistan by the end of 2014. “Our troops will continue to come home, and the war will end,” he said.

In fact, the war is unlikely to end. It may well accelerate as the Taliban seizes its chance to attack without facing American troops.

To say the war will end because U.S. troops are gone is like the toddler who imagines no one can see him when he closes his eyes. But it fits with the foreign policy of a leader who is on track, astonishingly, to preside over a sharp turn inward.

I say astonishingly because when he ran in 2008, Obama presented himself as a man who would lead the United States into a new era of international engagement, idealism and cooperation.

“We are heirs to a struggle for freedom,” he told a vast and enthusiastic crowd in Berlin in July 2008. “We are a people of improbable hope. With an eye toward the future, with resolve in our hearts, let us remember this history, and answer our destiny, and remake the world once again.”

Now, as the president told interviewers from the New Republic at the outset of his second term, “I am more mindful probably than most of not only our incredible strengths and capabilities, but also our limitations.”

The president is negotiating trade-opening agreements in Asia and Europe. He has maintained U.S. support for global health initiatives such as the fight against AIDS. He has traveled widely, negotiated a nuclear arms reduction with Russia, ramped up drone strikes and proclaimed a U.S. “pivot” toward the Pacific region.

But the dominant impression among foreign officials is of a policy of retrenchment. They see a steady reduction in the size of U.S. armed forces that will mean less ability to intervene and influence. They watched Obama withdraw all troops from Iraq, failing to negotiate an agreement that would have preserved some U.S. role in that now-unraveling country. They see him preparing to withdraw most — or all, his spokesman has said; the size of any residual force has not been announced — troops from Afghanistan.

The president boasts of his intervention to save the people of Benghazi from attack in 2011 and drive out the dictator Moammar Gaddafi, but the Libyan operation turned out to be a case study in the policy of limitations. Obama acted only when pressed by French and British allies and then insisted on withdrawal instead of committing to help a new government establish itself. The predictable result is an unstable country, riven by militias and posing an increasing danger to its neighbors through the spread of arms.

Syria is the prime laboratory of U.S. disengagement, and the experiment is not going well. From a peaceful democratic uprising two years ago to a civil war in which U.S. assistance could have been decisive last year, the conflict has degenerated into something so savage that it’s no longer clear what, if anything, might help.

The White House seems to assume that, whatever the lofty aspirations of Berlin, Obama’s governing approach is what Americans want and the country can afford. While acknowledging “very real and legitimate” humanitarian interests in Syria — some 80,000 people have been killed, and millions have lost their homes — Obama recently said his “bottom line” has to be “what’s in the best interest of America’s security.” Judging by conversations with his team, there’s also an assumption that such assessments were clear during the Cold War but are hopelessly more complex now.

But those judgments have never been easy. During the Cold War, too, Americans fought bitterly over the size of the defense budget, the wisdom of interventions and the morality of supporting unsavory but friendly dictators. Over the decades the country made terrible mistakes overseas. But U.S. engagement and influence also helped to gradually open the world to more democracy and more prosperity.

To reduce such engagement — to concentrate on “nation-building at home,” as Obama has put it — may seem the practical, hard-headed choice. But eventually the country always re-learns the lesson that as states such as Syria or Libya spin out of control, the danger is hard to contain.

In 2012, according to Freedom House, three countries became freer and more democratic, while 27 became less so — the seventh consecutive year of more declines than gains. That’s an unprecedented streak in the wrong direction — and not consistent with long-term, hard-headed U.S. interests.

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