Earlier this week, Senator Lindsey Graham, a hawkish Republican from South Carolina, used a Senate Armed Services Committee hearing to stage a theatrical display of his disdain for the Obama administration’s nuclear deal with Iran.

The most telling part of his time in the spotlight came when he pressed Defense Secretary Ashton Carter to declare who would win if the United States and Iran fought a war:

Here’s a transcript of the relevant part:

Graham: Could we win a war with Iran? Who wins the war between us and Iran? Who wins? Do you have any doubt who wins?

Carter: No. The United States.

Graham: We. Win.

Little more than a decade ago, when Senator Graham urged the invasion of Iraq, he may well have asked a general, “Could we win a war against Saddam Hussein? Who wins?” The answer would’ve been the same: “The United States.” And the U.S. did rout Hussein’s army. It drove the dictator into a hole, and he was executed by the government that the United States installed. And yet, the fact that the Iraqi government of 2002 lost the Iraq War didn’t turn out to mean that the U.S. won it. It incurred trillions in costs; thousands of dead Americans; thousands more with missing limbs and post-traumatic stress disorder and years of deployments away from spouses and children; and in the end, a broken Iraq with large swaths of its territory controlled by ISIS, a force the Iraqis cannot seem to defeat. That’s what happened last time a Lindsey Graham-backed war was waged.

But one needn’t be an opponent of the Iraq war to glean its basic lessons.

Hawkish pols have a tendency to harken back to the late 1930s exclusively, but one need only look to the eve of World War I (to the Czar in Russia and the German Kaiser, say) to see that two countries can and do fight wars that both end up losing.

A war against the U.S. would likely be a disaster for Iran. And rigorous attempts to game out such a conflict suggest that it could be very bad for the U.S. as well.

My colleague Peter Beinart has written about this:

Robert Gates, who led the CIA under George H.W. Bush before becoming George W. Bush and Barack Obama’s defense secretary, has said bombing Iran could prove a “catastrophe,” and that Iran’s “capacity to wage a series of terror attacks across the Middle East aimed at us and our friends, and dramatically worsen the situation in Iraq, Afghanistan, Lebanon and elsewhere is hard to overestimate.”  

Meir Dagan, who led Israel’s external spy service, the Mossad, from 2002 to 2011, has warned that an attack on Iran “would mean regional war, and in that case you would have given Iran the best possible reason to continue the nuclear program.” In the aftermath of a military strike, he added, “The regional challenge that Israel would face would be impossible.”

Says Jeffrey Goldberg, another colleague, “War against Iran over its nuclear program would not guarantee that Iran is kept forever away from a bomb. It would pretty much guarantee that Iran unleashes its terrorist armies against American targets.”

In 2004, my colleague James Fallows observed an Iran war game led by Sam Gardiner, a retired Air Force colonel who spent more than two decades conducting war games at the National War College and other military institutions––and whose prescience about aspects of the Iraq War, derived from simulations, came far closer to what happened than anything Senator Graham predicted.

Said Fallows:

The most important hidden problem, exposed in the war-game discussions, was that a full assault would require such drawn-out preparations that the Iranian government would know months in advance what was coming. Its leaders would have every incentive to strike pre-emptively in their own defense. Unlike Saddam Hussein's Iraq, a threatened Iran would have many ways to harm America and its interests.

Apart from cross-border disruptions in Iraq, it might form an outright alliance with al-Qaeda to support major new attacks within the United States. It could work with other oil producers to punish America economically. It could, as Hammes warned, apply the logic of "asymmetric," or "fourth-generation," warfare, in which a superficially weak adversary avoids a direct challenge to U.S. military power and instead strikes the most vulnerable points in American civilian society, as al-Qaeda did on 9/11.  If it thought that the U.S. goal was to install a wholly new regime rather than to change the current regime's behavior, it would have no incentive for restraint.

What about a pre-emptive strike of our own, like the Osirak raid? The problem is that Iran's nuclear program is now much more advanced than Iraq's was at the time of the raid. Already the U.S. government has no way of knowing exactly how many sites Iran has, or how many it would be able to destroy, or how much time it would buy in doing so. Worse, it would have no way of predicting the long-term strategic impact of such a strike. A strike might delay by three years Iran's attainment of its goal—but at the cost of further embittering the regime and its people. Iran's intentions when it did get the bomb would be all the more hostile.

Here the United States faces what the military refers to as a "branches and sequels" decision—that is, an assessment of best and second-best outcomes. It would prefer that Iran never obtain nuclear weapons. But if Iran does, America would like Iran to see itself more or less as India does—as a regional power whose nuclear status symbolizes its strength relative to regional rivals, but whose very attainment of this position makes it more committed to defending the status quo. The United States would prefer, of course, that Iran not reach a new level of power with a vendetta against America. One of our panelists thought that a strike would help the United States, simply by buying time. The rest disagreed.

Iran would rebuild after a strike, and from that point on it would be much more reluctant to be talked or bargained out of pursuing its goals—and it would have far more reason, once armed, to use nuclear weapons to America's detriment.

Lindsey Graham’s notion that the question of war between America and Iran is coherently reducible to “we win” or “they win” is facile, dangerous, and especially galling from a man who ought to have learned better from the last war he urged. Even the most severe Iranian losses would not necessarily mean that “we win.”