Israeli Prime Minister Benjamin Netanyahu has real reason to worry about Iran acquiring a nuclear weapon. The country has indeed been taking steps toward a warhead for years, often in secret. A nuclear-armed Iran would pose a greater threat to Israel — and to the Middle East as a whole — than it already does, by using its nuclear deterrent as cover for more bad behavior such as backing anti-Israel terrorist groups and supporting Shia militant groups. And it would increase the risk of accidental war and of terrorists acquiring poorly secured nuclear material

President Obama sees that danger as well; it's part of why he shares Netanyahu's determination for preventing Iran from getting a nuclear weapons program, even if the two leaders disagree sharply on the best way to do it.

But there is one danger of an Iranian nuclear program that you hear a lot about but is largely groundless: that Iran wants a bomb so that it can launch an unprovoked, suicidal war against Israel.

Netanyahu himself hinted at, though did not explicitly make, this argument in his Tuesday speech to Congress.

"The days when the Jewish people remained passive in the face of genocidal enemies, those days are over," he said, drawing one of several parallels between Iran and Nazi Germany as he spoke directly to Holocaust survivor Elie Wiesel, who was in the audience. "I wish I could promise you, Elie, that the lessons of history have been learned. I can only urge the leaders of the world not to repeat the mistakes of the past."

This is an odd argument. Were Iran to launch a nuclear strike against Israel, it would be suicide. Netanyahu knows this better than anyone; Israel has developed what is known as a second-strike nuclear capability specifically to deter this sort of threat. Even if Iran succeeded in surprising Israel with a nuclear attack, Israeli forces would still be able to retaliate (for that matter, so would the US), thus ensuring that Iran be utterly destroyed. There is no cost-benefit calculation by which an offensive strike would make sense for Iran.

The idea that Iran would want to launch a nuclear attack on Israel, then, rests on the theory that Iran's leaders do not operate like other heads of state, that they are so inherently irrational that they would deliberately sacrifice their own country and political system just to bomb Israel. As Newt Gingrich once put it, for example, "It's impossible to deter them. What are you going to threaten?"

Despite widespread misconceptions to the contrary in the US — often pushed by politicians who wish to play up the Iranian threat for political gain — there is no reason to believe that Iran wants to launch a suicidal, offensive nuclear strike against the US, Israel, or any other country.

This is the wide consensus among serious analysts of Iran. As Clifton W. Sherrill of Troy University explained in a 2012 issue of Nonproliferation Review, "It is highly unlikely that the Islamist regime plans to actually detonate a nuclear weapon in an offensive attack. Both of the obvious targets, the United States and Israel, have a second-strike nuclear arsenal capable of threatening the Islamist regime's survival."

Where did people get the idea that Iran's leaders have spent the last 36 years secretly plotting a suicidal war against Israel? There are two pieces of evidence that usually get presented — both of which have been debunked.

The first piece of evidence is the record of anti-Israel statements from some Iranian leaders, especially hardliner President Mahmoud Ahmadinejad, who did indeed say some very alarming things during his time in office. The translation of his most inflammatory statement — a 2005 statement that Israel's presence in Jerusalem should be "wiped off the map" — has been debated for years by academics and translators. But it is true that Iranian leaders reject the legitimacy of Israel's existence and that Ahmadinejad has been alarmingly eliminationist.

But Ahmadinejad did not set Iran's foreign or military policy — Supreme Leader Ayatollah Ali Khamenei did and does. Khamenei and Ahmadinejad famously and bitterly clashed for years, with Khamenei and his supporters criticizing Ahmadinejad's crazier rhetoric and ultimately isolating him within Tehran. The point is that Ahmadinejad was known for over-the-top rhetoric on all things. And while this was legitimately concerning, there was very little evidence his rhetoric about eliminating Israel represented Iranian policy and lots of evidence it did not. And in any case, he is now out of power and practically friendless in Tehran.

The second piece of evidence that Iran would launch a suicidal war on Israel is the idea that the leaders' interpretation of Shia Islam foretells of a messiah who will return on the apocalypse. While Ahmadinejad did reference this idea many times, he was alone in this, as Matt Duss of the Foundation for Middle East Peace explains, and was widely rebuked by Shia scholars and his own country's political and clerical establishments.

Actual readings of Iran's official Shia theology by actual religious scholars, Duss finds, reach the opposite conclusion that Newt Gingrich did: Iranian leaders see it as their religious duty to preserve their system, not destroy it in a fiery war with Israel. Many of those leaders, after all, spent years fighting to establish the Islamic Republic, then to defend it against Iraq's 1980 invasion and subsequent eight-year war.

As scholar Mehdi Khalaji told Duss, "As the theory of the guardianship of the jurist requires, the most significant task of the Supreme Leader is to safeguard the regime, even by overruling Islamic law."

Meanwhile, there is ample evidence that Iranian leaders are just as rationally invested in self-preservation as anyone else. You can't hold up a political system as complex and besieged as Iran's without being shrewdly self-interested. If Iran's Islamic regime were really looking for a suicidal war in which to martyr itself, the eight-year war with Iraq offered many such opportunities, none of which it took.

There are a number of reasons that Iran wants a nuclear program and has taken steps toward a nuclear bomb. Some of those reasons are rational and others are not. All of them are concerning. But a desire to launch an offensive strike against Israel, or the US, is not one of them.