The proposal of extending airstrikes into Syria to combat Daesh is under discussion today, with the vote occurring later. You can read the whole sorry 'debate' in the commons here. As for the particulars about whether or not we should be intervening, or on the nature of the evidence Cameron has provided to support his view that they would be supported by 70,000 moderate fighters  who would push back Daesh in Syria Septicisle covers it very well here and here.
I'm not going to get into this. Suffice to say I think that this is all putting the cart before the horse and that, with the United States and Germany looking to commit their troops to the ground, I suspect we'll be in for more than just airstrikes in the coming future. Corbyn is basically correct: until there is a political solution and an objective that we're working towards, very little is going to be achieved by dropping bombs on Daesh held territory. We'll kill a few of them, and probably a lot of civilians, but it won't actually succeed at anything until it's welded to a more concrete strategy. Getting the strategy sorted first would be the most important thing, then the intervention.
Instead, I'm just going to briefly go into the morality of it. My jumping off for this point is Cecile Fabre's article 'Mandatory Rescue Killings'. More specifically the thought experiment that she poses in it. Starting from the assumption that is morally permissible to kill someone in self-defence  she argues that in a scenario where a victim (V) is threatened by a morally culpable attacker (A)  and cannot defend themselves, then a rescuer (R) has the right to intervene and kill A on the behalf of V. This makes logical sense, after all if you are allowed to kill in your own self-defence then it does stand to reason that the right to kill in self-defence can transfer to someone who is capable of defending you when you are not.
Fabre's position is quite nuanced and the article itself is interesting (whilst she asserts that a person would have the moral right to intervene, it's not so clear that they would have the moral duty, or obligation to do so). What I want to take from this is it's relevance to humanitarian interventions. The logic, obviously, is clear in the Syria case: Daesh (the A) are killing Syrians and threatening others (the V), so we (the R) have a duty to intervene to protect them. As the Syrians, the civilians, are incapable of defending themselves their right of self-defence has transferred to us.
Obviously the case is a lot more complicated than this and many, many of these assumptions can be argued with, but I want to keep it to it's basics and just complicate it in one respect. If the victim has been attacked, and is injured as we might suppose, then if R intervenes and stops A, his obligations do not end there. After all, it'd be a funny sort of interventionist who dives in, kills the attacker, and then runs out to roar his triumph and beat his chest in victory for all to see, whilst quietly leaving V to bleed to death.
And yet this is the situation that we appear to be in. Nobody, after all, is making any kind of serious proposition towards what will happen after Daesh are defeated. The chaos of Syria would still be there and would still need to be resolved. It would likely need the interventionists to stay for a while, sort things out and promote a better future. But that isn't on the table. Indeed the precedent from Libya is worrying. What happened in Libya was exactly the scenario I described above: we went in, we stopped A (Qaddafi) then we ran away and shouted our triumph and left the Libyans to burn. Indeed the country is in such a state that you could make a plausible argument that Virgil was a time traveler who brought Dante to the future, not a spirit who took him on a tour of Hell.
This is the legacy of Blair and Bush. Say what you like about them, but at least they were prepared to stay and try and solve the problems in post-war Iraq (badly, but hey). Their successors, Cameron in particular, are wary of this having seen the political fallout and the cost. Public's loose interest in moral missions; and, unfortunately, interventions take a lot of time and money particularly when they're on a large scale. So, instead, they take the plaudits of going to war and doing something, but avoid the climb-down and the miseries of the aftermath. This is intervention without the responsibility that goes along with it.
Any intervention carries a responsibility to the people intervened on the behalf of, particularly in situations where they're already badly wounded and the place is chaotic. That responsibility doesn't stop with bombs. If we have a moral right and a moral duty to intervene, then we also have a moral duty to stick around and help make things better.
Remember that the next time some politician goes prattling on about what our moral obligations are.
 If they're anything like the Labour 'moderates' then that's a large barrel of dangerous fanatics we're dealing with here...
 A not incontestable assumption, but I won't get into it.
 That is, someone who is acting of their own volition and not at the behest of someone else, controlled by something, or out of their mind etc.