With the presentation of an unclassified briefing on Syria’s use of chemical weapons, the administration of President Barack Obama has put its cards on the table. As Secretary of State John Kerry said: “The primary question is really no longer, what do we know? The question is, what are we -- we collectively -- what are we in the world going to do about it?”

The administration’s intelligence assessment carries the unwanted burden of the George W. Bush administration’s meretricious effort to justify its 2003 invasion of Iraq -- and for many, that will be enough to disqualify it. Yet taken at face value, it is a compelling and disturbing document.

With a high degree of confidence, the U.S. intelligence community asserts that Syrian chemical weapons personnel were active in the three days leading up to the Aug. 21 attack; that a senior Syrian official worried about the attack being detected; and that afterward the Syrian military intensified its artillery barrage on the affected areas, probably to destroy traces of the assault. The assessment puts the death toll at 1,429, including 426 children.

Obama called the attack “a challenge to the world,” but repeated that he hasn’t made a final decision on his response. That decision was made harder by the vote in the U.K. House of Commons blocking the government of Prime Minister David Cameron from joining any military action.

Nonetheless, the logic of Obama’s position that the U.S. is seeking to defend an international norm demands that he redouble his efforts to build an international coalition. That is all the more important given Kerry’s accurate assessment that “Russian obstructionism” means the United Nations “cannot galvanize the world to act, as it should.” Nations such as Turkey and organizations such as the Arab League need to show solidarity with more than just tough talk. And Obama would be wise to publicize Syria’s barbaric behavior at next week’s Group of 20 meeting in Russia, the home turf of Syria’s biggest backer.

Obama would also be wise to secure the support of Congress -- with a vote. Not because the president must, but because in a democracy, the people’s representatives deserve a say in such matters. More pragmatically, without domestic support, a limited strike will lack the full moral and political force it needs to be effective.

That brings us to our final injunction: Obama needs to spend less time reassuring Americans that there will be no boots on the ground and more time explaining why they have skin in the game. Yes, Americans are war-weary. And yes, they’re neuralgic about global norms and conventions.

But stopping the use and spread of chemical weapons is not just an abstract principle the world should aspire to. It is of practical, life-saving importance to all of the world’s citizens. Just ask the residents of the suburbs of Damascus.

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