At bottom, the decision to strike at the regime of Syrian President Bashar al-Assad for its use of chemical weapons rests on a straightforward proposition: Assad violated an almost century-old international norm against the use of these barbarous weapons and must be made to pay a price to keep him and others from using them again.

Yet the administration of U.S. President Barack Obama has given so many conflicting explanations of its reasoning that it has undermined its domestic and international support.

Yes, the criticism has been partly fueled by partisan politics at home (witness the pirouetting logic of Republican strategist Karl Rove, whose comments on Obama’s Syria policy should be taken with an Iraq-sized grain of salt). Yet the larger problem is that the White House is trying simultaneously to ease the conflicting concerns of anti-war Democrats and anti-interventionist Republicans on the one side and, on the other, hawks and aggressive internationalists who want strikes to tip the balance in Syria’s civil war.

Obama needs to find a more effective way forward on Syria with his speech scheduled for tomorrow night. Rather than continuing its game of policy Twister, which threatens to land the administration flat on its face, how about focusing on the (relatively) simple issue of chemical weapons? While he’s at it, he would do well to avoid some of the administration’s more distracting arguments.

The president might start by dropping any World War II analogies. With all due respect to Secretary of State John Kerry, this is not our “Munich moment.” And Obama was likewise ill-advised to compare the hesitancy of Americans on Syria to the reluctance of many Americans to help the U.K. in the early days of World War II. If your professed plan is a limited military operation, why invoke memories of a global conflagration?

Moreover, today’s Syria is not 1940s Germany: It is a tiny, backward nation with a relatively insignificant military. And Assad is not Hitler: He has no nightmarish visions of global conquest, among other things. But he has amassed a huge chemical arsenal, while 98 percent of the world is committed to getting rid of theirs, and he has shown less and less compunction about using it. That’s case enough for not letting him go unpunished.

Next, as much as the administration wants to woo hawks, it should resist the temptation to pitch any military response as a means to tip the balance in Syria’s civil war. That includes burdening the speech with a discussion of plans for delivering more support to Assad’s opponents. Doing so will scare off more supporters than it gains and make it hard to define what constitutes a successful strike. As the administration recognizes, the intractability of Syria’s underlying conflicts and its sectarian fissures ultimately demand a political settlement. That’s why, as we’ve argued, this mission should be about chemical weapons, not regime change.

And please stop talking about how “war-weary” the American people are and how any U.S. military operation in Syria won’t resemble the wars in Iraq and Afghanistan. Spend more time on telling the people what the mission is, and why it’s important, and less on what it’s not and why this time will be different -- a declaration that doubters are unlikely to believe anyway.

Finally, the president need not spell out, at this point, what he will do if he fails to secure congressional support for a strike. Revealing his ultimate course of action would effectively let Congress off the hook. This may not be America’s Munich moment. It is, however, a time for its elected representatives to make a clear choice based not on flawed arguments or antipathy toward the president, but on a clear-eyed assessment of the threat and the need to do something about it.

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