Low Probability but High Impact Events: Black Swans in the U.S.-Iran Relationship

Assessing black swan events involving the United States, Iran, and the Middle East is a potentially fraught enterprise.  There are many different points of friction that exist between the parties, informed by a history that has both good and bad chapters. Moreover, U.S. policy itself is sufficiently in flux that it is possible decisions or actions that would have constituted black swans a decade ago are—now—a reasonable expected outcome of what’s in play. Still, when it avoids going into the realm of speculative fiction, black swan analysis has significant utility in identifying not only low likelihood risks but also analytic weak points and information gaps. It can also point to opportunities that might otherwise be hidden.

At the outset, it is useful to exclude some events that, while plausible black swans in the past, should not be assessed as such today. I can identify four:

• War between the United States and Iran
• War between Israel and Iran
• A deal between the United States and Iran
• The death of Supreme Leader Ali Khamenei

For the first two, there is already a decent chance of war, if we define war in this context to be a state of militarized hostilities. Indeed, as relates to Israeli-Iranian war, it is unclear what would be different in any practical sense between what Israel and Iran have already done over the last year given their physical distance. Even if there were to be a material change in hostilities, short of nuclear attack, the differences between what has happened and what could happen are modest. This term is also used colloquially rather than implying a formal declaration of war by the U.S. Congress or equivalent step. War would not need to involve an attempted invasion of Iran by the United States. But, in this category, I would include routinized attacks by U.S., Israeli, and Iranian forces against their adversaries and undertaken over a period of time.

As for a deal, the United States and Iran have already demonstrated an ability to conclude a deal and to implement it for a period of time. The leadership of both countries have espoused a desire for negotiations, even if there is a considerable trust deficit.

The last exclusion may strike some as peculiar, though not because it assumes that Khamenei will, in fact, die at some point. Not even the most ardent Khamanei fan has yet claimed he is immortal. Instead, this event has long been the short-hand for the political uncertainty that will exist in his absence.  

After all, Khamenei has been the supreme leader of Iran for most of its existence, succeeding Ruhollah Khomeini in 1989. Khamenei’s death will shock the system and open up political space that has rarely existed in the Islamic Republic of Iran. But, in my view, predictions of tremendous upheaval in Iran after Khamenei’s death presuppose the absence of a plan and process to handle it. The unexpected death of Ebrahim Raisi in a May 2024 helicopter crash should prompt some pause in this assumption. Raisi was replaced temporarily by First Vice President Mohammad Mokber and thereafter by Masoud Pezeshkian through snap elections held over the summer. Similarly, Iran has rules in place for what will happen when Khamenei dies and a structure for selecting a new supreme leader. Who that person will be and how they will wield power are, at present, unknowable, but the result is likely to be something closer—at least in the first few weeks and months—to a variant of the current system than its wholesale rewriting. In fact, I would go so far as to argue that it is likely another older man will be selected to serve in Khamenei’s place while, underneath his aegis, the powerbrokers of the Iranian system jockey among themselves for influence and control much as they have for decades. And, in fact, even if Khamenei were to die and the result was chaos, this has been a largely consensus hypothesis for years from which I’m now diverging; it is hard to argue, in that context, this as a black swan event.

Those four events excluded, what would constitute a black swan event? I can see three that would constitute truly low probability, high impact events, the first and third of which I outlined at the workshop and the second one that I found persuasive from another presenter.

• Natural disaster leading to collapse in regime governance, either directly or as a result of a subsequent attack
• Iranian regime collapse, led by rejection of security forces to use violence to enforce national discipline
• An Iranian nuclear weapons test that results in a cascade of nuclear weapon tests along alliance lines

For the first, Iran exists on a tectonic fault line and has experienced significant earthquakes in the not-too-distant past. The Bam earthquake in 2003, for example, left 34,000 people dead along with hundreds of thousands more injured or displaced. Iran has also experienced adverse weather events, such as flooding and landslides. That weather or seismic activity could occur and cause disruption is not, itself, a black swan event, even if it is impossible to predict when, where, and how this would manifest. But, what makes this a black swan at this point is the pronounced tensions that exist presently as well as the U.S. sanctions regime, making it far less likely that there would be an outpouring of humanitarian relief for Iran on this occasion. It is in fact far more likely that, should Iran experience a significant natural disaster, the impulse among some in the U.S. leadership to take advantage to seek the collapse of the Iranian regime.  

Even without external intervention, Iran’s regime may not be capable of sustaining control after a significant natural disaster. The Iranian economy remains weak and its levers of political control have in recent years been even more militarily pronounced. An Iran that is responding to a natural disaster may be too preoccupied to exert political control using its security forces, especially if they were compromised themselves in the disaster. This could be doubly the case if a disaster were to implicate an Iranian government project, such as the Bushehr Nuclear Power Plant, which itself was constructed in a seismically vulnerable part of Iran. 

This speaks to the second black swan event, that of a regime collapse caused by the security forces being unwilling or able to reinforce societal control. The other presenter described this scenario as stemming from a decision that security forces would not exert will over anti-regime protestors, such as those who took part in the “Woman Life Freedom” movement starting in 2022. This scenario was described as reminiscent of the Egyptian security forces unwillingness to fire on protesters in Tahrir Square in 2011, but there are historical analogues to the Iranian Revolution against the shah. To date, security forces have been willing to exert force against Iranian dissidents and protestors, but if they did not (at least in some large scale), then this would constitute quite a significant black swan event.

The third scenario is one of a more international bent, that of a major change in how nuclear weapon tests are treated by the international community. Over the last 30 years, nuclear weapon tests have been rare and condemned almost universally. The United Nations Security Council (UNSC) met in 1998 to condemn India and Pakistan’s nuclear weapon tests equally, as it did in 2005 (and often thereafter) when North Korea tested nuclear weapons. Its failure to do so again would constitute a significant breach with the past and, more troublingly, a signal that the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and nonproliferation regime were irretrievably breaking down. It is almost certain that, after an Iranian nuclear weapon test, there would be considerable pressure on Saudi Arabia and the UAE to develop their own nuclear weapons. But, one of the constraining forces against this would be the risk of international opprobrium that it would bring.  

Today, it is far too easy to see a breakdown in this order, with the United States, Russia, and China signaling to their respective partners in the Middle East a readiness to look past nuclear weapons development in furtherance of geopolitical power bloc enhancement. In fact, it strikes me as plausible that there would be a willingness on the part of large parts of the international community to accept the inevitability of future proliferation, not least out of recognition that Iran’s own work had a security basis in the threat it was facing from at least one nuclear-armed state. 

With these three scenarios in hand, it is worth considering what types of work and analysis could be done now to better prepare for these black swans. For the first two, more counterfactual analysis as to the nature of the regime and—especially—areas that may constitute brittleness in its support and construction would be warranted. It would be useful to understand better the vulnerabilities of the system to collapse and to game out how a regime change scenario would be addressed by the United States and its partners. Particularly in the context of natural disaster preparation and response, it would be appropriate for the United States and its partners to consider how they would react in these scenarios.

As for the third, even as the United States and its partners refuse to accept the possibility that Iran will test nuclear weapons (as Iranian nuclear weaponization has been long deemed “unacceptable”), it would be useful for the United States to at least consider how it would respond in this circumstance. This should include consideration of how to engage Iranian partners in Russia and China, and signals that they should be encouraged to send in advance of any such test to discourage one. This could include, for example, discussion with Russia and China about how the international community would respond to nuclear weapons programs emerging in other states. 

Black swans are, by their nature, rare but examining them identifies fault lines and tensions in existing policies and practices. It is an exercise that ought to be repeated.