A couple of weeks ago, 50 religious conservatives publicly stated that the U.S. must "destroy" IS. (Russell Moore, about whom I recently wrote, here, was one of those 50.) That sounded a lot like a questionable call for a holy war.
. . . where there is an unjust aggression, I can only say this: it is licit to stop the unjust aggressor. I underline the verb: stop. I do not say bomb, make war, I say stop by some means. . . . To stop the unjust aggressor is licit.