Even IF every attack is preceded by a warning, that doesn't mean every warning is followed by an attack. Some could be mere bluster.
Very true. This letter was quite a grandiose thing to do, however. Of course we all hope this is just bluster, though.
This is true, but one must plan and prepare, and even act, as if the attack is coming. For one thing, that tends cut on the bluster from the next megalomaniac who is thinking of declaring he wants to kill infidels.