My friends assured me that Hitler's talk was sheer bombast,” Vishniac said in 1955. "But I replied that he would not hesitate to exterminate those people when he got around to it. And who was there to defend them? I knew I could be of little help, but I decided that, as a Jew, it was my duty to my ancestors, who grew up among the very people who were being threatened, to preserve - in pictures, at least - a world that might soon cease to exist.