Secretary of State Mike Pompeo gives a press briefing at the State Department on Thursday on the attack on two oil tankers near the entrance to the Persian Gulf. (Andrew Harrer/Bloomberg)

Why war with Iran might be less likely than you think.

Last week, an attack on two tankers in the Gulf of Oman raised tensions between the United States and Iran — on the heels of a similar attack in May. Though Iran denied responsibility, Secretary of State Mike Pompeo said intelligence evidence showed Iran was to blame, and President Trump concurred that “Iran did do it.” Although questions remain in some quarters about the attack’s nature and source, on Sunday on CBS’s “Face the Nation,” Rep. Adam Schiff (D-Calif.) said the evidence Iran was responsible is “very strong and compelling.”

As was true when the United States and North Korea exchanged bellicose rhetoric in 2017 and early 2018, many are now worried that the U.S. and Iran are heading for war. When Trump was warning that North Korea faced “fire and fury” if it threatened the United States, we wrote about why, despite the rhetoric, war was unlikely.

This time, some factors are indeed pushing the two sides toward conflict. But forces of restraint are also reducing the likelihood of war.

Tensions can lead to a “spiral” of escalation.

Both the United States and Iran say that they do not want a war, but that they are prepared to fight if the other side starts one.

What’s worrisome is what political scientists call the spiral model of conflict escalation. Sometimes, when countries take measures they think will improve their own security, potential opponents can perceive that as threatening — a classic security dilemma. Those potential opponents then take measures to improve their own security — which the first country sees as threatening. And so on. When countries do not trust each other, and perhaps even fear that the other side wants war, they are unlikely to believe conciliatory signals from the other side, and nobody wants to appear weak. The result is a spiral of conflict.

The past few weeks’ events have certainly ratcheted up tensions. The recent tanker attack and America’s decision to quickly blame Iran only raises them further. And as Tyler Jost and Rob Schub wrote here at TMC last month, the Trump administration’s decision-making process could make it even more difficult to navigate the tricky problem of reading and responding to signals in a crisis like this.

War would be very costly in this case.

A conflict between Iran and the United States could be very costly. For instance, in such a war, Iran might use mines to keep ships from traveling through traffic in the Strait of Hormuz — a crucial, narrow passage for world energy supplies. If that happened, the U.S. options for clearing the mines would be complicated and costly, as Caitlin Talmadge argues. Such an operation might require hitting targets inside Iran or risk Iranian retaliation from coastal positions given the narrow geographic chokepoint — all pointing toward further escalation. Knowing this, the United States might instead choose to go straight to a bombing campaign. But coercive bombing might also lead to escalation.

Despite these dangers, there are still important constraints on both sides.

Misperception rarely causes war.

The spiral model may not be the right way to think about how conflicts escalate. Missed signals and miscalculation can indeed generate tension. But leaders have many ways to avoid conflicts that they do not want to fight. The historical record suggests that misperception and accidental escalation rarely lead to war — as Dan Reiter noted here at TMC during the height of North Korea tensions in 2018.

Domestic political pressures don’t seem to be pushing toward war.

The United States and Iran also face domestic pressures that may make both sides hesitate before escalating. Iran’s economy has suffered under the Trump administration’s renewed sanctions, and parliamentary elections are coming up. Although the country’s president, Hassan Rouhani, has used tough rhetoric recently, a costly war might not benefit Iran’s leaders, since it could inflict further economic and human costs, or even lead to regime change or collapse.

Likewise, after nearly two decades of war in the Middle East and Afghanistan, Americans are unlikely to welcome another major conflict. Neither Trump’s own party nor the opposition Democrats has rallied the U.S. public to pressure Trump to escalate. As TMC’s Michael Tesler noted in December, although Trump’s base supporters tend to have hawkish views, they supported his decision to withdraw troops from Syria. If Trump does not want war with Iran, his base would likely follow.

The president doesn’t seem eager for war.

There has been much talk about a replay of the Iraq War, with the United States using possibly flawed intelligence to justify war.

But although Trump has used limited military force in Syria, he seems generally opposed to costly wars in the Middle East, and unlikely to embrace a new one. Both Pompeo and national security adviser John Bolton are much more hawkish on Iran, but Trump has distanced himself from his advisers’ hawkish rhetoric, particularly the most costly option: regime change.

Here’s what to watch for.

So which will win out: the risks of escalation or the pressures for restraint?

Amid all the tension, Iran wants its regime to survive, and Trump probably does not want to absorb a costly war. In the coming days and weeks, it will be telling to see if there is further daylight between Trump and his advisers.

Here’s one more risk: if Trump’s hawkish advisers present an option that seems like it could be kept limited, but actually carries a strong likelihood of escalation. Trump has embraced limited displays of force, such as airstrikes in Syria in 2017 and 2018, and he issued a threatening tweet on Iran in May. But he has also pivoted away quickly from harsh rhetoric to diplomacy before — as he did toward North Korea — and has already achieved his campaign goal of pulling out of the nuclear deal he disdained.

The bottom line: Despite rising tension, powerful factors reduce the likelihood of war between the U.S. and Iran. That’s unlikely to change anytime soon.

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Michael C. Horowitz (@mchorowitz) is professor of political science and the associate director of Perry World House at the University of Pennsylvania. He is the co-author of “Why Leaders Fight.”