ISIS (a.k.a. Islamic State of Iraq and Syria, or increasingly Islamic State) is no less a threat to Klal Yisrael than were the Communists or Nazis. Again, from a “this world” perspective, our survival will largely depend on the Americans (without whom the Third Reich would rule the world today, or the Communists would have achieved the global dictatorship). While we would undoubtedly survive an Islamic conquest, just as we would have survived a thousand year global Reich, or a global “dictatorship of the proletariat” – suffice to say we’ll have more to worry about than which hecksher to buy and where to go on vacation.
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While the above deals with “this world” (the world of ???), frum Jews deal more with the world of ??? and have no option other than to concentrate on Torah and Mitsvos and allow Ha-Shem to take care of matters.