There's not much point in us adding to the bombs that the USA are currently dropping on Syria. The Yanks aren't having that much success, except when they work with Kurdish forces on the ground -- The Kurds are their only significant ally on the ground, until they eventually give up with the idea of over-throwing Assad. They spent $40-$50 million training and equipping 'moderates' and they managed to retain all of 5 (yes, five) fighters. It's why all the bombs dropped so far haven't significantly weakened ISIS, except when they can get the Kurds on the ground to help.
It's why Russian bombs are (apparently) being more effective, as they are working with the Syrian government forces on the ground, who are in turn bolstered by Iranian forces and Hezbollah fighters. They are targeting the anti-government forces too, but ISIS are taking hits as well. They say that you can't win a war from the air alone. I'd imagine that's even more difficult when you aren't actually attacking a nation state.
So, in the end, we (The West) are going to have to take the deal that Russia came up with in 2012 -- leave Assad in place for the time being, help the Syrian government to stay in control and then everyone, together, targets ISIS. We could add some bombs at that stage, but with Russia and America on the case, it's a bit like bringing a pack of sparklers to a fireworks display. America wasn't interested back then because they were convinced Assad would be over-thrown, but Russia and Iran have decided otherwise. Right now, there is more scope for compromise on their part.
I think the latest attacks by ISIS will weaken their position in Syria because Russia and America will reach a compromise over Assad, and then most of the guns will get turned on ISIS as a result. So when Corbyn, or anyone else, talks of a political settlement, this is what they mean. They aren't talking about getting ISIS around the table, because they obviously have no interest in that.
