During my recently completed term as US special envoy to monitor and combat anti-Semitism, one question was posed to me with greater frequency and urgency than any other. I heard it in English, I heard it in French, I heard it in Hebrew, Russian, Italian. Even when I didn’t speak the language of the questioner and no translator was at hand, I understood the gist: “Is the global situation of the Jews today as dire as what we faced in 1933?” It’s a question that carries particular resonance ahead of Holocaust Memorial Day on Tuesday, the 81st anniversary of the...