Subsequently, the United States will be correctly perceived by all sides as intervening on behalf of the armed opposition. From there, it is easy to conceive how the initial limited intervention for humanitarian purposes – like Libya in 2011 – turns into a joint campaign plan to assure that Assad is toppled.
Since almost everyone concedes that the planned strikes are virtually useless , it is hard to believe that the administration won’t feel compelled to launch additional attacks on the Syrian government when the first strikes  fail to change regime behavior. There will presumably be increasing domestic and international pressure for an escalation of U.S. involvement once the U.S. begins attacking Syria, and once Obama has agreed to take direct military action of one kind he will have greater difficulty resisting the pressure for even more. There is also always a possibility that Assad and his patrons could retaliate against U.S. forces or clients, in which case the pressure to escalate U.S. involvement will become much harder to resist. The U.S. is rarely in the habit of bombing a foreign government without sooner or later being drawn deeper into a larger conflict with it. Watching Obama’s creeping interference in Syria’s civil war over the last year gives me no confidence that he would be able to resist demands for future escalation.
It goes without saying that any military strike on Syria at the present time won’t be legal. It will probably have consequences for other U.S. interests that aren’t being considered right now. Far from boosting U.S. credibility with Iran, this will almost certainly undermine negotiations and increase tensions with Tehran. If U.S.-Russian relations were deteriorating before now, they will get much worse once the U.S. starts attacking Syria, and that could affect cooperation on any number of other issues. Launching attacks on their client will be sure to intensify Iranian and Russian paranoia about U.S. motives, and that could easily have undesirable effects in the months and years to come.