What most advocates of ground troops in Syria conveniently forget to mention is what is to be done áfter Daesh is militarily defeated.
They keep coming up with Petraeus' Surge. And yes, the surge did defeat Al-Qaeda in Iraq. But only temporarily. They came back with a vengeance and renamed themselves, in the end, to Islamic State.
The reason they give for it is that Obama retreated the troops. But one should not forget the American people were pretty fed up with the war at that point in 2009 and the Iraqi's preferred to see them go too, prompted by the Iranians. (Not to mention Bush signed the SOF agreement to retreat the troops)
Defeating Daesh militarily is the fairly easy part. Just bring in a lot of troops, Surge style, and you could do it. In that sense the likes of Max Boot and Michael Doran are right. But what they neglect to mention is what is to be done afterwards.
Sunni's in Iraq will not trust the Baghdad government in the foreseeable future and the Shiite dominated government is not one for power sharing. Not with the Kurds and certainly not with the Sunni's who have suppressed them in the Saddam years.
In Syria there is not even a beginning of a solution. Even if the Alawite regime, with or without Assad, could come to some sort of agreement with the rebels, the rebels themselves are very fragmented. And even on the regime side groups like the Druze are increasingly disgruntled. Imposing democracy on a heavily armed and very divided country is not very likely going to result in a stable government.
And in the current fast media culture Western countries are not for staying in a situation for the long haul. And even if we do, like the 14 years we have been in Afghanistan, the results are less than convincing.
And then there is the effect Western troops have when they are deployed in the region. They work as a jihadi magnet. Al Qaeda was founded by Bin Laden as an reaction to US deployment in Saudi-Arabia in 1990/91.
What you would need is a local solution with local Sunni forces so the population would have a decent alternative to Daesh or other jihadist. The problem is which Sunni power would be able or willing? Turkey is more interested in fighting Kurds, The Saudi's are more interested in fighting Iran. Not to mention the fact that any regional power moving in will immediately face opposition from the others.
What is needed is a sort of agreement between the regional powers Saudi-Arabia, Turkey and Iran. But that's a long way off but the very first small step has been made in Vienna: Iran and Saudi's sitting at one table and talking.
Regarding IS the only thing you can do now is contain them for the time being and that is going better than expected. One could argue that IS spreading out to Europe is a sign of that. Last year they weren't interested in exporting terrorism. They were expanding their caliphate. Now that expansion has been checked they fall back on old Al-Qaeda tactics: international terrorism. Quite a shift in strategy.
There won't be any quick fixes for the current terrorism wave. European terrorism doesn't even come from Syria although Hollande likes to make us believe that. It is home grown. They are EU nationals, born and bred. Radicalized in Europe. But that is a message that is too inconvenient for most.