Historically (at least for the past couple of hundred years), the problem is that if the Pope ends up speaking out loudly and calling on nations to act, a lot of people die.
His predecessor called for German Catholics to not allow themselves to be wooed by the Nazis (Mit Brennender Sorge) resulted in an increase in persecution against Catholics throughout Germany.
Consider: the Vatican never ran a crusade by itself. It depended upon Catholic Kings and Princes to supply troops for a crusade.
Seriously, consider: if +Francis was to call for a crusade, which countries would rise to the call?
Would the United States? Certainly not under Obama, but would the US under Bush respond? Not only would the atheistic left pillory Bush for responding, there are a good portion of conservatives that would do the same thing...including a whole host of FReepers who would say this was some sort of conspiracy for the Vatican to take over the world.
Would Great Britain? Less likely than the US.
Would France? Less likely than the UK.
Would Germany? Chuckle...
I agree that it is horribly frustrating to only see crocodile tears, but if there was a call for more, who would listen? You and I might. However, I can't speak for you, but I don't "own" an army.
An infuriating and bloody mess we find our world in.
Sad that the fate of so many may lie in the hands of a Russian wannabee Tsar and maybe the Chicoms.
And any divisions the Pope would have; all have their hands out looking for freebies.
At one time, the Pope had an army...