Across The Red Line Evidence of a brutal chemical attack in Syria poses a defining test to the U.S.'s reputation and to Barack Obama's foreign policy vision

Foreign policy grants American presidents almost supernatural powers. From thousands of miles away, they can mobilize fleets and squadrons at a whim, sometimes killing without risking a single soldier's life. But foreign policy can also become a curse, with an equally mystical ability to ruin a presidency. Barack Obama learned that lesson watching his predecessor wage what Obama famously called "a dumb war" of choice in Iraq. His opposition to the invasion launched the one-term Senator's first presidential run, and he arrived in the White House with a clear vision of a humbler America narrowly focused on core interests, like healing domestic economic and social wounds. Obama would hunt down terrorists in caves and deserts and throw a harder punch at the Taliban in Afghanistan. But he also presented himself as a conciliator, a peacemaker who would land the Nobel Peace Prize before he'd even redecorated the Oval Office.

From the start of his presidency, Obama sounded his call in speeches from Washington to Prague to Cairo, describing a transformed world order--"a revolutionary world" where "we can do improbable, sometimes impossible things." Cynics said Obama was just putting a gloss on harsh economic reality: deep in debt and with its financial sector in a tailspin, the U.S. couldn't afford an interventionist foreign policy. But Obama seemed genuine enough when he spoke of starting a dialogue of "mutual respect" with Iran, and to other rivals, he vowed that "we will extend a hand if you are willing to unclench your fist." Reason would replace raw power, and the neoconservative vision would be retired. It was hope and change on a global scale.

But history, it has turned out, wasn't interested.

The fists remained clenched, the rhetoric toward the U.S. was disrespectful, and although there was revolution from Cairo to Tripoli to Damascus, it often unleashed dangerous religious and tribal passions across the Middle East. The hope has fermented into fear, the change into danger. Now, in a region that has confounded Presidents for decades and where the security stakes are highest, Obama faces a defining test in Syria.

This is not where Obama wanted to be. On Aug. 22, one day after a cloud of what is suspected to have been nerve gas descended on a Damascus suburb, killing hundreds of people, the President left the White House for an all-smiles bus tour of upstate New York, focused on college affordability. But that morning in the Situation Room, Obama's national-security team was grasping the shocking scale of the attack and its implicit challenge to American power and authority.

In a bitter irony, the attack had come on the one-year anniversary of Obama's warning that the use of chemical weapons by the Syrian regime constituted a "red line" that, if crossed, would have "enormous consequences." Video footage showed ghastly images of the dead, including women and infants, who almost seemed fortunate compared with the spasming, frothing survivors. As Obama was briefed on his presidential bus, it became clear that he too was facing the prospect of military action in the Middle East over weapons of mass destruction.

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