So the standard Libertarian foreign policy doctrine regarding military intervention is: do not use the US military unless the US or our close allies are in immediate danger. We should not be invading and occupying every third-world shithole and deposing their dictator because our media aren't comfortable sipping over-priced white wine on their designer leather couches, at their Georgetown cocktail parties while watching unpleasant images of far away conflicts and humanitarian crises.
I generally agree with that.
That said, Libertarians are hesitant for the US military to return to Iraq or Syria to deal with ISIS, because it might mean yet another long-term, outrageously expensive occupation of one or both of those countries. I sort of agree with that also. But here's where I depart from the hard-core Libertarians:
Because many American and British citizens have gone to fight with them and could one of these days return using valid passports, even more radicalized than when they left, ISIS does represent, in my view, a gathering threat against the US and Great Britain, far more so than Al Qaeda or the Taliban......I mean if you ever believed that Taliban was a threat......I do not. For these reasons, the Bush doctrine of taking the fight to the enemy on their land rather than waiting for them to come here is a valid one in this case.
Here is my caveat to the Bush doctrine: Send in a limited, specialized force who, along with a tactical drone strikes, kill as many ISIS fighters, especially the American and British nationals, with extreme prejudice. Take care of business and get out. No occupation. No nation building. No election monitoring. No building schools or bridges or power plants. No nothing except killing as many ISIS guys as we can find as fast as possible, then come home.