From the time that the peaceful protests in Syria turned into an armed uprising, it has been reasonable to argue that any imaginable outside intervention would do as much harm as good. I have made that argument myself. But the situation on the ground has changed, and so the calculus of outsiders must change as well. U.S. President Barack Obama's administration should accept that the only desirable outcome in Syria is a victory by the rebels and should work much more actively than it has both to hasten the day of that victory and to avoid the terrible settling of accounts that might well accompany such an outcome.
It is true that Syrian forces have committed terrible atrocities in recent weeks, both in the house-to-house killings in the Damascus suburb of Daraya and in aerial bombardments of civilians waiting in bread lines in the northern city of Aleppo, which have been documented in an appalling video recently posted by Human Rights Watch. But the moral case for intervention became incontrovertible many thousands of deaths ago. What has changed is the practical case.
Many people who supported the intervention in Libya, including officials in the White House, have opposed comparable action in Syria out of concern that escalating hostilities could turn an insurgency into a full-blown civil war, inflaming sectarian hatred and threatening neighbors with massive refugee flows and ethnic and religious tension. But almost all those things have come to pass simply as a result of the demons Syrian President Bashar al-Assad has unleashed.
The war has already escalated to previously unimaginable levels. The Syrian regime is now engaging in the strategy of counterinsurgency-by-atrocity used so effectively by Sudan against the people of its south and Darfur -- intentionally killing large numbers of civilians in order to shatter the opposition's will. Assad has sown the seeds of sectarian hatred by unleashing largely Alawite forces against Sunni civilians, in turn making Syria into a new crusade for Sunni extremists, many of them crossing the border from Iraq. And he has exported the conflict beyond Syria's borders, with Sunnis and Alawites facing off in the streets of Tripoli, Lebanon's second-largest city. The greatest danger to Syria and the region now comes from allowing Syria's civil war to continue unabated.
If the calculus of potential harm has changed, so too has the calculus of potential good. A no-fly zone would have done nothing to stop the thugs and soldiers who carried out the massacres in Daraya. The regime, however, doesn't have enough troops to repress the rebellion everywhere at once. Assad has been deploying helicopters and jets in Aleppo, Idlib, and elsewhere in the north not only to terrorize civilians but to prevent the rebels from establishing control over a large swath of territory, as the Libyan opposition did in Benghazi. The rebels have begun to shoot down a few of the government's helicopters and jets, but Assad is still counting on aerial terror to subdue the region. A no-fly zone might not stop the killing, but it could give the rebels the foothold they desperately need.
And unlike in Libya, where it was clear from the outset that NATO planes would have to take on Muammar al-Qaddafi's tanks and armored personnel carriers, a no-fly zone extending perhaps 75 miles south of the Syria-Turkey border could turn the tide in Syria.