One year after the commons vote, America and others began dropping lots of bombs. It didn't remove the Syrian government, and then the Russians joined in on the other side. If America and others started bombing in 2013, imo it is highly likely the Russians would have joined the party earlier and protected the Syrian government. Remember, the Syrian civil war started in 2011 -- when the Syrian government eventually needed them, Russia stepped in.
To pretend that it's Labour's fault is very silly. It's far more complicated than that. And even in a pretend world where Russia and Iran don't help the Syrian government and, in 2013, David Cameron flew a spitfire over there and killed Assad himself, hastily replacing one group of loons for another doesn't necessarily work out either -- see Libya. It's gambling, not a sure-fire, black and white, can't fail plan.