Yale historian Timothy Snyder is indebted to Israeli Prime Minister Benjamin Netanyahu, who recently made Snyder’s new book even more newsworthy than his extraordinary scholarship deserves to be. And Netanyahu is indebted to Snyder, whose theory of Hitler’s anti-Semitism is germane to two questions: Is the Iranian regime’s anti-Semitism rooted, as Hitler’s was, in a theory of history that demands genocide? If so, when Iran becomes a nuclear power, can it be deterred from its announced determination to destroy Israel?

Netanyahu recently asserted, again, that a Palestinian cleric was important in Hitler’s decision to murder European Jews. Netanyahu said that on Nov. 28, 1941, when Hitler supposedly preferred to expel Europe’s Jews rather than exterminate them, Haj Amin al-Husseini, Grand Mufti of Jerusalem, met with Hitler and urged him to “burn them.”

Certainly the Mufti favored genocide; he certainly was not important in initiating it. Mass murder — the Holocaust — accompanied the German army, especially after the September 1939 outbreak of war, and especially after the June 1941 invasion of the Soviet Union. Granted, it was not until the January 1942 Wannsee Conference that the “final solution” became explicit. But by the time Hitler met the Mufti, approximately 700,000 Soviet Jews had been shot. Snyder, not Netanyahu, should be heeded concerning the Holocaust’s genesis.

Attempts to explain Hitler’s obsession with Jews began with the idea that he was unfathomable, a lunatic “Teppichfresser” (carpet chewer). The comforting theory was that no theory can explain Hitler because he was inexplicable, a monster, a phenomenon without precedent or portent.

In 1996, however, Daniel Goldhagen’s book “Hitler’s Willing Executioners: Ordinary Germans and the Holocaust” argued that the explanation for the genocide was acculturation — centuries of German conditioning by the single idea of “eliminationist anti-Semitism.” This cognitive determinism reduced Hitler to a mere catalyst who unleashed a sick society’s cultural latency.

This drew a rejoinder from Christopher Browning, author of “Ordinary Men” (1992), a study of middle-aged German conscripts who became consenting participants in mass-murder police battalions in Poland. Browning noted that protracted socialization — centuries of conditioning — could not explain the Khmer Rouge’s murder of millions of Cambodians, or the Chinese’ slaughter of millions of Chinese during Mao’s Cultural Revolution.

What happened in those places proved the power of an idea — Marxism understood as a mandate to extirpate “false consciousness” — to legitimize, even mandate, mass murder. In “Black Earth: The Holocaust as History and Warning,” published in September, Snyder argues that the Holocaust’s origins have been hidden in plain sight, in ideas Hitler articulated in “Mein Kampf” and speeches.

Snyder presents a Hitler more troubling than a madman, a Hitler implementing the logic of a coherent worldview. His life was a single-minded response to an idea so radical that it rejected not only the entire tradition of political philosophy but the possibility of philosophy, which Hitler supplanted by zoology.

“In Hitler’s world,” Snyder writes, “the law of the jungle was the only law.” The immutable structure of life casts the various human races as separate species. Only races are real and they are locked in mutual and unassuageable enmity, in Hitler’s mindset, because life is constant struggle over scarcities — of land, food and other necessities.

One group, however, poisoned the planet with another idea. To Hitler, says Snyder, “It was the Jew who told humans that they were above other animals, and had the capacity to decide their future for themselves.” To Hitler, “Ethics as such was the error; the only morality was fidelity to race.” Hitler, who did not become a German citizen until 11 months before becoming Germany’s chancellor, was not a nationalist but a racialist who said “the highest goal of human beings” is not “the preservation of any given state or government, but the preservation of their kind.” And “all world-historical events are nothing more than the expression of the self-preservation drive of the races.”

Now, assume, reasonably, that Iran’s pursuit of a potentially genocidal weapon will not be seriously impeded by parchment barriers such as the recent nuclear agreement. And assume, prudently, that the Iranian regime means what it says about Jews and their “Zionist entity.”

Then apply Snyder’s warning: Ideas have consequences. The idea of anti-Semitism is uniquely durable and remarkably multiform. It can express a mentality that is disconnected, as in Hitler’s case, from calculations of national interest.

Hence an anti-Semitic regime can be impervious to the logic of deterrence. Much, including Israel’s calculation of what military measures are necessary for its safety, depends on the nature of Iran’s anti-Semitism.

© 2015, Washington Post Writers Group