As we went to press at midweek, a U.S. airstrike on Syria seemed all but certain. Now we brace for its possible aftermath.

There are some good arguments for the United States and its allies taking military action. After years of bloody civil war that have left more than 100,000 dead and created more than 1 million refugees, Syria’s brutal dictator Bashar Assad last week crossed what President Barack Obama called a “red line,” deploying chemical weapons on his own people, killing hundreds. U.N. inspectors are in Damascus collecting evidence of what the rest of the world already understands as terrible fact.

The world cannot stand idly by in the face of such an atrocity. And having drawn that red line so clearly, the president cannot retreat from it without appearing weak and vacillant.

However, this is the Middle East, the world’s most volatile powder keg. Thus, we urge maximum caution before the administration takes this fateful step.

Should the attack take place, Syria and Iran have threatened to retaliate by launching rockets against Israel. These would not be the crude Kassams of Hamas, but precision-guided missiles capable of hitting Tel Aviv or anywhere else in Israel.

And were Syria and Iran to let fly their arsenals, who’s to say Hezbollah in Lebanon and Hamas in Gaza would not get in on the action? Israel could face the most massive bombardment in its history, with a potential for mass casualties.

Israel says it is ready, but can it ever be so? And if Israel were to retaliate harshly, as its leaders say it would, might this not unleash the doomsday scenario we all dread?

Some Israeli officials doubt Syria or Iran would really fire on Israel. We hope they are right, just as we hope any U.S. strike will be swift, surgical and manageable.

But the specter of unintended consequences thrives in the fog of war. If we weaken Assad, we thereby strengthen the rebels, many of whom appear to be jihadists aligned with al-Qaeda and no friend to America.

The world acknowledges that the use of chemical weapons must not go unpunished. As the world’s only superpower, the United States has the responsibility and the capability of meting out that punishment, and is being given the green light by our allies and by the Arab League.

If we do strike, let our message be clear: This is a limited strike against specific targets. It is not a call to war, and any Syrian retaliation aimed at broadening the conflict — particularly and specifically any Syrian move against Israel — will not be tolerated.