Sorry, just back in and I'm putting my hands up for poor geography, but not resileing the position.
Try collective adventures in Iran, Iraq, Libya, Mali, Sudan and Afghanistan, with drone attacks on Yemen, Somalia and Pakistan for good measure. In common with this Syrian proposition, none of them with any overarching objectives, just tactics, and none with a robust exit strategy.
The idea that we now wade into a civil war within which other sectarian and regional proxy wars are being played out for a whim or a posture - I'm discounting "principle" here as we're still arming the Egyptian military coup that killed at least five hundred people recently, though granted not with gas - is imo plain bonkers.