If you want to read a cautionary tale about whether Israel will attack Iran, I suggest Kurt Eichenwald’s “500 Days,” which is not about that question at all. It describes how a determined George W. Bush took the United States to war in Iraq. “This confrontation is willed by God, who wants us to use this conflict to erase His people’s enemies before a new age begins,” Bush told a bewildered French President Jacques Chirac. For some reason, Chirac thought Bush sounded fanatical.

Benjamin Netanyahu is not one who sees himself willed by God to take on Iran — he is much too secular for that — but there is ample reason to think he sees himself as the savior of the Jewish people, what the Israeli novelist David Grossman has called his “megalomaniacal” vision. Netanyahu insists that Iran is developing a nuclear weapon to most likely use against Israel. He points to the repellent anti-Semitic and anti-Zionistic statements of Iranian President Mahmoud Ahmadinejad and, most chillingly, to analogous statements made by Adolf Hitler. For a time, few took Hitler seriously, either.

I pay some heed. The Holocaust is too monstrous a crime to be easily dismissed. Seventy percent of Europe’s Jews were murdered, and much of the world, preoccupied and not all that upset, did little about it. The charge of complicity, of apathy, of heroic indifference, applies not just to the nations of Europe but to the United States as well. In 1939, as the Jews of Europe were running for their very lives, an emergency bill to admit 20,000 Jewish children as refugees was defeated in Congress. President Franklin Roosevelt’s cousin Laura Delano Houghteling summed up the national mood with a dinner party quip: “Twenty-thousand charming children would all too soon grow into 20,000 ugly adults.” (Her comment was discovered by the historian Rafael Medoff in the papers of the diplomat Joseph Grew at Harvard.)

What happened once can happen again. Anti-Semitism infects the brain; it is a kind of tertiary-stage syphilis that induces madness. To deny the Holocaust is madness. To vow the elimination of a state is madness. But to pursue a nuclear weapon at the cost of harsh economic sanctions may or may not be madness. After all, Iran suffered about 1 million casualties in the war with Iraq that Saddam Hussein started in 1980. It cleared minefields with children promised the toy of martyrdom. It, too, pays homage to history.

Netanyahu cannot rid himself of the past. It comes through his father, the historian Benzion Netanyahu, who was a scholar of anti-Semitism. It comes through the militant ideology of Ze’ev Jabotinsky, a pariah in his own day, something of a prophet in our own. It comes at him tactilely by thumbing through family picture albums — all those relatives, innocently smiling for the camera, and then gone when the page is turned. History is Netanyahu’s daily briefing book.

But things have changed. Israel has been created, recognized and armed to the teeth. Above all, it has a sworn ally. The president of the United States vows that Iran will not be permitted to develop a nuclear weapon. Ahmadinejad plays cute with Iran’s intentions, but on CBS News last week he waxed rationally: “Let’s even imagine that we have an atomic weapon, a nuclear weapon. What would we do with it? What intelligent person would fight 5,000 American bombs with one bomb?” The man is starting to make some sense.

For almost a year, Netanyahu has been hinting that he will strike Iran’s nuclear installations. The consensus in the U.S. intelligence community is that Israel can do some damage and possibly delay the program; it cannot end it. The consensus in the Israeli intelligence community is the same. In contrast to the silence of the U.S. intelligence community (including retired military men) as Bush was preparing to rid Iraq of weapons it did not have, Israel’s retired intelligence chiefs have been leaking and shouting their disagreement with Netanyahu. An airstrike someday, maybe — but not now. The din has been striking.

The story of Bush’s march to war in Iraq shows how one man, enthralled by his own vision, can persist until, in exhaustion, his opposition collapses. Netanyahu knows what he wants. But there is still time for Iran to back down before President Obama’s red line — no nuclear weapon — is crossed. This is a war whose time has not yet come.