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The war with Iran has prompted many questions about what comes next. Will the Islamic Republic regime survive? What could replace it? Will Iran dissolve into chaos? What does this all mean for the Arab Gulf states, Israel, Iraq, Lebanon, and the rest of the region? What are the near-term, medium-term, and long-term risks and opportunities?

The White House has said that the war will last four to six weeks, but what if it goes well beyond that? What if the United States and Israel have unleashed a chain of events that is beyond their control? A worst-case scenario is that Iran descends into a chaotic civil war — with competing armed factions and separatist movements — that drives sustained high oil and gas prices, triggers a massive refugee crisis, destabilizes the region, fuels new or reinvigorated terrorist movements, and fundamentally undermines U.S. influence globally. While this might not be the most likely outcome, it nonetheless warrants consideration.

The Value of Worst-Case Scenarios

The war with Iran raises many valid questions and potential contingencies. When we are faced with so much uncertainty, scenario planning provides a helpful tool to think through multiple potential futures. Scenario planning can come in many forms, but the purpose is usually to help an organization — public or private sector — prepare for a range of possibilities. It provides an opportunity to test how well its resources, procedures, and policies would perform in different situations and to assess what changes it might need to make.

There are various methodologies, but all require some degree of imagination. In most exercises, scenarios should all be plausible, but they should not all be likely. Best-case and worst-case scenarios seldom represent the most likely futures, but they provide crucial bookends for testing some of the outer limits of plausible outcomes. In my experience working with businesses and government agencies, there is often a tendency to focus on the middle — more likely — scenarios or the best-case scenario. This reflects a cognitive bias for what feels like the most rational outcomes or the one that people hope for. There often is a tendency to dismiss the worst-case scenario, which may be because people don’t want it to happen or because they’re trying to show that they are not alarmist.

However, worst-case scenarios are important to think through. When done well, they are plausible and therefore could realistically happen, even if they don’t represent the most likely outcome. Planning is incomplete without thinking through how a worst-case scenario could play out.

Today, the war in Iran opens the door to many potential outcomes, and policymakers and other stakeholders should think through them all. Here I describe one plausible worst-case scenario: a full collapse of governing authority in Iran and a descent into civil war. This scenario is focused primarily on a two year timeframe but considers implications to a five year horizon.

The Scenario

Civil War in Iran

U.S. and Israeli strikes early in the war kill or incapacitate most of the Islamic Republic’s top officials and leaders. While the survivors initially attempt to display unity, they quickly lose control of the country and splinter into competing groups. Anti-regime protests break out across the country to overthrow the government and succeed in taking over various prisons and government institutions. The military experiences increasing defections.

However, none of these groups coalesce into a movement sufficiently capable of filling the power vacuum. Soon, factions of the former regime, different protest movements, and remnants of the military begin fighting each other — sometimes turning into armed criminal groups as much as political movements. Some groups seek to control oil and gas facilities and other sites with significant economic value, especially those with raw resources that are relatively easy for smugglers to exploit.

In the chaos, ethnic minority groups that have long sought increased autonomy take their opportunity. Some of them have arms and try to assert their authority over areas where they have a demographic majority. The most notable of these are the Kurds in Iran’s western areas neighboring Iraq and Turkey and the Balochs in Iran’s eastern areas neighboring Pakistan and Afghanistan. In both places, low-level separatist movements predate the civil war and quickly ramp up into far more significant armed conflicts.

Some other ethnic minority groups try to seize greater autonomy, including some members of Arab communities in Khuzestan province and parts of Azeri communities — the largest ethnic minority in Iran — in the north. The Arab communities lack the level of armed resistance that parts of the Kurdish and Baloch minorities have and focus more on stabilizing their local areas and nurturing longer-term hopes for some degree of autonomy. The Azeri minority is initially less ready to engage in separatist violence, but an increasingly assertive Azerbaijan works to foment separatism among Azeris in the north, with the eventual goal of incorporating part of Iran’s northern territory into a larger state of Azerbaijan.

Regional Spillover

The intense instability and violence quickly spill over neighboring states. The Iranian Kurdish uprising immediately creates both opportunities and problems for northern Iraq’s Kurdish Regional Government, where Iranian Kurdish dissidents have long sought shelter. Prior to Iran’s civil war, the Turkish government was working to end its long-running conflict with the Kurdistan Workers’ Party, and in March 2025, the group declared a ceasefire and later said it would disband. However, when the war in Iran began, implementation was moving along slowly and uncertainly. The resurgent separatist movement among Iranian Kurds threatens to breathe new life into Kurdish nationalism, derailing the fragile deal between Ankara and the Kurdistan Workers’ Party. Similarly, in Syria, the uprising among Iran’s Kurds undermines the efforts of the government in Damascus to reach terms with the Syrian Democratic Forces. As Iran’s Baloch insurgency gains steam, it strengthens Baloch insurgent groups in Pakistan and increases insecurity for the Baloch community in Afghanistan. The border areas between the three countries have a long history of security problems, occasional clashes, and cross-border trafficking, and the chaos in Iran intensifies them.

Instability in Iran threatens to exacerbate other conflicts along its borders. Azerbaijan encourages separatism among Azeris in Iran, hoping to expand its control into bordering parts of northern Iran. The peace deal between Armenia and Azerbaijan holds, given Azerbaijan’s dominant position, and the loss of Tehran as a friend further weakens Armenia. Fighting between Pakistan and Afghanistan was intensifying before the war in Iran, and the increased insecurity in Baloch areas and along the countries’ borders with Iran — plus a wave of Iranian refugees — further fuels the conflict. Iraq’s government struggles to maintain stability, as it copes with spillover effects from the war, including difficulty exporting oil.

There is a huge flood of refugees out of Iran. To understand the scale, consider that Syria’s civil war sent more than six million refugees fleeing the country between March 2011 and December 2024 — mostly to neighboring states but also into Europe. The influx to Europe created a socio-political crisis that fueled far-right political parties and created political cracks within the European Union. Syria’s population at the start of the war was more than 22 million people, and Iran’s population at the start of its war was more than 91 million people. Millions now flee to states such as Afghanistan, Pakistan, Iraq, and Turkey — all of which have already struggled to absorb refugees from other conflicts and which experience varying levels of fragility. Armenia, Azerbaijan, and Turkmenistan also receive refugees.

Some refugees attempt to cross the Caspian Sea or Persian Gulf or otherwise transit to third countries, causing flows into Europe, the Arab Gulf states, Russia, Central Asia, and beyond. Members of the Iranian diaspora in Europe and the United States try to assist friends and family in immigrating. At a time when the global treaties, norms, and processes for managing refugee crises are nearly broken, the Iran refugee crisis breaks them.

Civil war and chaos in Iran increase the risks to Syria as it attempts to recover from its own brutal civil war, which in turns increases the risks to Lebanon, as it tries to recover from years of instability and to disarm Hizballah. The regional chaos and security risks arising from civil war in Iran further set back any — admittedly small — hope of progress toward Israeli-Palestinian peace, as regional countries and global powers are too distracted to invest the necessary attention and resources. The regional chaos offers Israel opportunities to consolidate its control over the West Bank and Gaza, as well as its presence in southern Lebanon and southern Syria — strengthening Israel’s sense of security in the short term but increasing instability over the longer term.

Piracy becomes a major problem in the Persian Gulf and Arabian Sea. Competing Iranian political factions overlap with criminal networks and use available resources — including some of the small, armed boats that the Iranian regime had prepared for military purposes — to pursue piracy as a source of revenue. Piracy and general insecurity negatively affect transportation through the Strait of Hormuz and surrounding waters. All these factors create challenges for the Arab Gulf countries’ plans for economic diversification and growth, especially for the transportation, logistics, and tourism sectors.

Global Spread

History suggests that chaos in the Middle East risks sparking new terrorist movements or reinvigorating old ones. The war in Iraq created fertile ground for the rise of the Islamic State, which also benefitted from the civil war in Syria. Instability and war in Yemen has offered space for the Islamic State and al-Qaeda. Lebanon’s civil war and Israel’s invasion gave birth to Hizballah, the 1979 revolution in Iran created a government with the means and interest to support it, and regional instability over the years provided Hizballah with many opportunities to grow its influence. The mass displacement of Palestinians in 1948 led to the development of Palestinian terrorist groups. Now, the growing regional insecurity provides fuel to both Sunni and Shiite terrorist movements, with negative consequences in the region and beyond.

Economic consequences are multifaceted, including driving up oil and gas prices over a sustained period and undermining regional growth. The maritime shipping industry must adapt to new risks. The influx of refugees particularly strains Europe’s fiscal environment, as well as its social and political cohesion.

China and Russia find it ever easier to promote a narrative that the United States is a reckless, unreliable, and irresponsible actor. While the U.S. military has demonstrated its extraordinary power, the aftermath of the war convinces much of the world that Washington breaks things and then doesn’t want to own the responsibility. Many countries, especially in Asia, reluctantly see Beijing as a safer, albeit domineering, option than Washington. Russia benefits economically from the increase in oil and gas prices, at least early in the war.

Ukraine, still at war with Russia, comes under increased pressure to make concessions to Moscow, as European countries grow reluctant to support Kyiv while trying to manage a new refugee crisis and an increasing feeling of insecurity. The United States — worried about its own munitions, focused on the war in the Middle East, and losing interest in Ukraine even before the war with Iran — has already halted its support for Ukraine, and Europe fails to fill the gap.

Preparing for the Worst

All the elements of this scenario are debatable. And that’s the point. The process of going through a worst-case scenario — and taking it seriously but not as an inevitability — helps to understand which aspects are more likely than others, and how different actors can prepare or what they can do to avoid a terrible outcome.

There are plausible scenarios that are far more optimistic — even ones that include chaos and war within Iran. For example, chaos in Iran might mean that Hizballah must concede to pressure in Lebanon and disarm, which could help stabilize Lebanon and improve its relations with Israel.

But a civil war in Iran is a plausible scenario, and most of the likely outcomes would have negative consequences for peace, stability, and prosperity in the Middle East and around the world. The war will affect the interests of many stakeholders, ranging from private sector companies to governments around the world. All these stakeholders should be thinking through worst-case scenarios now. U.S. policymakers might yet be able to take action now to avoid an incredibly destabilizing outcome. Policymakers from other countries and business leaders need to consider how to protect their interests and mitigate their risks, in case the worst comes to pass.

Kerry Boyd Anderson is a membership editor at War on the Rocks. She previously provided political risk analysis on the Middle East and global security issues to private and public sector clients and wrote a weekly column for Arab News. She received an M.Sc. in international relations from the London School of Economics and Political Science and a B.A. in global studies from the University of Iowa. All opinions stated here are her own.

Image: Hossein Zohrevand via Wikimedia Commons