The idea of a pre-emptive American attack on Iran periodically resurfaces in Washington, despite the absence of any strategic logic. After abating following the 2015 agreement to limit Iran’s nuclear program, the war drums are beating again, with the Trump administration ratcheting up the pressure. Is striking Iran an option?

Iran is a longstanding and steadfast opponent of the United States. It promotes terrorism, extremism and instability in the Middle East, with brutal allies like Syrian President Bashar al-Assad and Lebanon’s Hezbollah. The Iranian regime continues to develop advanced weaponry while repressing internal dissent. There is no question that the United States, its partners in the Middle East and Europe, and many Iranians themselves would prefer a different government than the theocratic one that has held power since 1979. But the idea of a pre-emptive American attack on Iran, which periodically resurfaces in Washington, would be a monumental mistake.

The United States has had military encounters with Iran for years around the Middle East, but the more recent wave of support for a pre-emptive strike came earlier this decade, as Tehran expanded its ballistic missile capability and appeared on track to develop nuclear weapons. After the 2015 international agreement known as the Joint Comprehensive Plan of Action, or JCPOA, placed strict limitations on Iran’s nuclear program, the war drums abated for a while. But now they are beating again.

John Bolton, President Donald Trump's national security adviser, has long advocated a more hawkish U.S. policy toward Iran. In a 2015 op-ed, he openly supported bombing Iran’s nuclear facilities. Soon after joining the Trump administration, Bolton asked the Pentagon for military options to strike Iran. Earlier this week, unnamed Trump administration officials—possibly looking to develop a legal rationale for a military strike—suggested to reporters in The Washington Times that Iran is providing sanctuary to senior al-Qaida operatives. As Steven Cook wrote in Foreign Policy, this all looks ominously like what the George W. Bush administration did in 2002 and 2003 to justify military intervention in Iraq.

It is possible that the Trump administration is simply ratcheting up the pressure on Tehran, but there is also a chance that it intends to attack. To do so in the absence of clear Iranian military aggression would constitute one of the greatest fiascos in American foreign policy, destroying U.S. leadership around the world and probably igniting another wave of violence in the Middle East that provokes more extremism.

A pre-emptive American attack would be illegal under international law, technically making Trump a war criminal. While the United Nations Charter allows collective or individual self-defense by member nations, Iran’s current regional aggression and weapons programs do not constitute a legal basis for war. When President George W. Bush intervened in Iraq in 2003, he argued that the United States was implementing U.N. Security Council resolutions. While this was a contentious position, it was enough to prevent the United States from being universally seen as a criminal aggressor. A pre-emptive attack on Iran now would not even have that kind of thin legal justification.

Absent direct aggression by Tehran against the United States or one of its allies, an illegal American attack would destroy Washington’s ability to promote a rules-based international order and shatter many—perhaps most—of America’s already damaged security partnerships. Trump would be a pariah to most nations. The United States would face censure, possibly even economic sanctions. Even if militarily successful—by degrading Iran’s ballistic missile arsenal, for example, or weakening the regime—the strategic benefits of an attack would pale in comparison to the costs. By any measure, it would be a massive political loss.

Rather than weakening the theocrats in Tehran, striking Iran would solidify their power and instantly discredit their internal opponents.

In fact, it is hard to discern any strategic logic in the idea of a pre-emptive strike on Iran. Since all indications are that Tehran is complying with the conditions of the JCPOA, an attack would clearly show that Washington is not interested in peaceful methods to limit Iran’s nuclear program. America, which is already considered the primary threat to peace in many parts of the world, would be seen as a bully, signaling to the Iranian regime that it must have nuclear weapons to stop further U.S. aggression. And many other nations around the world would explicitly or tacitly agree. A pre-emptive attack, then, would actually increase the chances of a nuclear Iran.

A U.S. military strike also would compel even Iranians unhappy with their government to rally behind it. Nothing pulls a nation together like an external attack. Rather than weakening the theocrats in Tehran, American military action would solidify their power and instantly discredit their internal opponents.

Even if Iran is providing sanctuary to al-Qaida leaders, as that recent Washington Times report suggests, there is no way to make a case that it poses enough of a threat to the United States to justify the strategic costs of a military strike. Most of the world would see such an attack based on that thin argument as illegal aggression.

A pre-emptive attack on Iran would not make the United States safer or advance its interests. In fact, it would be the exact opposite of Trump’s stated “America First” policy, by benefiting only Saudi Arabia and Israel, the two countries pushing for Trump to strike Iran, and further damaging America’s influence and security partnerships around the world.

What if American military action somehow succeeded in pushing the Iranian regime out of power, as the Trump administration wants? The result would be a civil war even worse than the catastrophic ones in Syria, Iraq and Libya. After Iraq, one might think that Americans have learned that toppling an authoritarian political system without a legitimate and effective substitute in place, and a major international peacekeeping mission, can only lead to disaster. But apparently not everyone in Washington has learned that lesson.

A pre-emptive U.S. military strike on Iran would ultimately be one of the worst strategic blunders in American history. That it is repeatedly considered by serious political leaders and security experts remains incomprehensible.

Steven Metz is the author of “Iraq and the Evolution of American Strategy.” His WPR column appears every Friday. You can follow him on Twitter @steven_metz.

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