The answer lies with Muslims themselves. Specifically, it means that Muslim religious leaders around the world must announce that any Muslim who deliberately targets non-combatants for death goes to hell.
I arrive at this answer based on something that I have long believed about Pope Pius XII and the Holocaust.
I readily acknowledge that the situations are not the same. The Jews of Europe were not annihilated by Catholics in the name of Catholicism; whereas the Christians, Muslims and Jews who are massacred by Islamic terrorists are murdered by Muslims in the name of Islam.
I also readily acknowledge that many of the attacks on Pope Pius XII for his alleged inaction and even collaboration with the Nazis during the Holocaust are animated by individuals who hate Western religion generally or hate the Catholic Church specifically. Pius XII was not "Hitler's Pope," as one best-selling book on Pius XII is titled.
Moreover, Pius XII lived in Italy during World War II, in a fascist dictatorship that began as Hitler's ally and ended up being the target of Nazi atrocities. This was not the case with President Franklin D. Roosevelt, for example, who lived in the safety of a free country six-thousand miles away from Germany, did nothing to save the Jews of Europe, and even sent a boatload of Jewish refugees from Hitler back to Europe. Yet the critics of Pius are silent about Roosevelt.
Nevertheless, Pius could have done more to at least slow down the Holocaust. And I say this recognizing that Italy's Catholic clergy saved many Jews, and that Pius, to his credit, had to be aware of this. What he could have and should have done was to announce that any Catholic -- and any Christian for that matter -- who in any way helps in the murder of innocent Jews is committing a mortal sin and will not attain salvation. In other words, he or she will go to hell.
This would have had no impact on the many Germans and other Europeans who had no belief in God or religion; but it would have had an impact on many who did.
Dennis Prager is a SRN radio show host, contributing columnist for Townhall.com and author of his newest book, “The Ten Commandments: Still the Best Moral Code.”