WaPo: "In trying to help Syria, an intervention would destroy it"

"... Assad would remain defiant in the face of an attack. It is not as if he is constrained now, but he would probably step up the violence both to exert control within his country and to demonstrate that the United States and its allies cannot intimidate him. At the same time, the regime’s Iranian patrons and Hezbollah supporters would increase their investment in the conflict, meaning more weapons and more fighters pouring into Syria — resulting in more atrocities. And on the other side, Syrian opposition groups would welcome a steady stream of foreign fighters who care more about killing Alawites and Shiites than the fate of the country. This environment would heighten Syria’s substantial sectarian, ethnic and political divisions, pulling the country apart.
The formidable U.S. armed forces could certainly damage Assad’s considerably less potent military. But in an astonishing irony that only the conflict in Syria could produce, American and allied cruise missiles would be degrading the capability of the regime’s military units to the benefit of the al-Qaeda-linked militants fighting Assad — the same militants whom U.S. drones are attacking regularly in places such as Yemen. Military strikes would also complicate Washington’s longer-term desire to bring stability to a country that borders Lebanon, Turkey, Iraq, Jordan and Israel.
Unlike Yugoslavia, which ripped itself apart in the 1990s, Syria has no obvious successor states, meaning there would be violence and instability in the heart of the Middle East for many years to come...."