Americans, polls say, are souring on their nation's role as the world's policeman. President Obama's Tuesday speech to the United Nations General Assembly suggested that, after five years of mixed military experiences abroad, he, too, is growing more uneasy with the use of U.S. military might overseas.

That's not to say that he's stepping away from the crises roiling around the world. Obama committed to aggressive diplomatic pushes to prevent Iran from building nuclear weapons and to forge a peace deal between Israel and the Palestinians — two commitments that some experts expect to define his foreign policy for the remainder of his presidency.

Call it the evolution of the so-called Obama Doctrine, says David E. Sanger at The New York Times. In his first term, Sanger says, Obama's overseas policies were marked by a willingness to use force in cases where the U.S. faced a direct threat — but he was far more eager than his predecessor, George W. Bush, to avoid long, drawn-out conflicts with questionable national-security benefits.

Now, says Sanger, Obama has "absorbed some bitter lessons" about the limits of American power — most recently from the way his party deserted him over striking Syria, and before that by the way Libya descended into chaos after our bombing stopped. He insists he won't let Iran get nukes on his watch, Sanger says, but with the Obama Doctrine in flux and Obama's willingness to use force rattled by five years of mixed results, the question is "whether the Iranians believe him."

To Obama's detractors, Obama's foreign policy isn't evolving. It's "schizophrenic," says Elliott Abrams at The Weekly Standard. He appears all for freedom, human rights, and democracy, in principle, Abrams says, but, in practice, his willingness to cut diplomatic deals with tyrants offer nothing to people like the Iranians. He promises they'll be better off if their leaders go down the path of diplomacy, Abrams says, but in reality he's just leaving them at the mercy of a hated theocracy.

Not a word about living in freedom — not even as an aspiration. So the obvious conclusion any Iranian must reach is that if the regime does a nuclear deal, Mr. Obama is content to see the Iranian people live under tyranny forever. [Weekly Standard]

One shift in Obama's focus was unmistakable. The U.N. speech was almost entirely devoted to the Middle East — Obama only mentioned China once. That, says John B. Judis at The New Republic, means that Obama, who announced a "pivot to Asia" two years ago, has pivoted again, and plans to stake his foreign policy for the rest of his presidency on Iran and the Israeli-Palestinian conflict.

Pulling off a rapprochement with Iran, Judis says, could be the diplomatic motherlode, making peace possible in Syria, easing negotiations between Israel and the Palestinians, and giving the U.S. a new ally against terrorism. In that sense, Judis says, Obama might have just delivered the most important foreign policy speech of his career.

The danger of a turn back toward Realpolitik is that Obama will abandon even a declaratory attempt to promote human rights and the stirrings of popular rule in the Middle East. But in respect to Obama's willingness to deal with Iran and to throw America’s weight behind a resolution of the century-old Israel-Palestinian conflict, Obama's new turn could lead to astonishingly positive results in the Middle East. Jim Mann, the author of The Obamians, the best introduction to Obama's foreign policy, cautioned me the other day against accepting the image of second-term presidents as lame ducks. In foreign policy, Ronald Reagan and Bill Clinton achieved their greatest successes in their second terms, and the same may turn out to be true of Barack Obama. [New Republic]