Fools rush in. . .
The war in Syria never was primarily about the fate of Assad's regime. Assad is not the only domino on the table.
An excerpt from, "The Race To Raqqa Is On - To Keep Its Unity Syria Must Win" by b, Moon of Alabama, February 11, 2016:
The Saudis would fight under the control of the one brigade of the 101st airborne that was not announced to go for Mosul. The Saudis would deploy from Saudi Arabia likely via a U.S. controlled airstrip in west Iraq towards Syria while the brigade from the 101st would probably deploy from the Kurdish area in north Iraq through the Kurdish areas in north-east Syria towards Raqqa. Raqqa would thereby be attacked from a north-eastern and a south-eastern. The airport of Rumeilan/Abu Hajar would be one of the major supply bases.
Such a move of forces would be quite large and over relative long distances. But most of the area is desert and modern motorized military equipment could easily cover those distances in a day or two. This would put Saudi troops into Syria. If they would take Raqqa or Deir Ezzor and the eastern Syrian oilfields they would NEVER let go of it unless Syria would bend to the Saudi demand of introducing an Islamist led government.
The plan is workable but it would also instigate a large mobilization of Shia forces and could lead to a bigger conflict. The Russian Prime Minister Medvedev warned today that new Arab forces entering the Syrian war could spark a much wider war.