Robert Royal notes that a need to deal with actual violent threats means considering the relationship between moral and spiritual aims and secular force:

We need action on multiple fronts: diplomatic, ideological, social. But the clearest signal the West could send at the moment would be to put a contingent of special forces on the ground (preferably with, but if necessary without, Arab allies), drive ISIS out of Mosul, and keep it out. A military reversal of that magnitude would eliminate a fair bit of ISIS’s current glamour and open up a space for the longer-term soft approaches.

(source: Defending “Rome” – The Catholic Thing)

…and, of course, that’s not something that the Vatican seems to be very good at, these days.  But I can’t help myself; this makes me think of a favorite bit of half-serious whimsy from one of my favorite columnists, the self-described not-very-religious Jew who nonetheless cites Chesterton in the national press better and more often than just about anyone else, Jonah Goldberg:

I no way, shape or form would want to see a Catholic version of Jihadi terror (nor do I think such a thing would be remotely plausible). But it’s worth keeping in mind that we are already in an era of armed transnational religious movements. The problem is that they are evil. What would be so terrible about leading by example? Papal peacekeepers could do incredibly valuable work in parts of Africa or South America, protecting persecuted populations, delivering aid etc. The teaching effect could be profound (and perhaps very good at getting people back in the pews). Democracies are often slow and reluctant to do such work. And, if present trends continue America is going to do less and less of such things. Papal armies could do the jobs Americans won’t do. 

(source: The Pope Needs Ninjas)

OK, I admit, I find it hard to seriously imagine the Vatican actually taking on an extraterritorial military role.  But it’s worth remembering that there is, indeed, a place where the gears of ecclesial and secular authority mesh; they don’t live in separate spheres.

Because I’ve been so jocular about this, I’ll give Royal the last word: 

Here in Rome, there seem to be few who want to face that reality. It’s curious that as Europe, America, and the world confront such a clear enemy to human civilization, that there’s been little sense of urgency about acting in self-defense, let alone – as just war theory has always taught – to protect others who are innocent. It’s a serious question what this means about Christianity in our day, our secular order, and the world’s real moral priorities.

(source: Defending “Rome” – The Catholic Thing)