There is no plausible reason for the United States to go to war with Iran, although the Trump administration appears to be preparing to do so. In mid-May, the Pentagon presented the White House with plans for deploying up to 120,000 troops to the Middle East to respond to Iranian attacks on US forces or the acceleration of Iran’s nuclear weapons program.

To be sure, the Iranian government is guilty of genuine transgressions against American interests and values. It backs Syria’s brutal dictator, Bashar al-Assad. It undermines the security of Israel by organizing and sustaining Shia militias in Syria, supporting the Palestinian extremist group Hamas, and arming the Lebanese Shia militia Hezbollah. By serving as Iran’s proxy on Israel’s border, Hezbollah exposes Lebanon—long a fragile state—to the risk of Israeli retaliation. Iran has also supported Shia militias in Iraq that in theory answer to the Iraqi prime minister through a special commission, but in practice are outside the national military command structure, which compromises the cohesion and authority of the Iraqi state.

With money and weapons, Iran backs the Houthis, an insurrectionist movement in Yemen that has ousted the elected government and attacked the territory of its Saudi patrons. It has allegedly tried to stir Shia unrest in Sunni-ruled Bahrain, where the US has an important naval base, and in the Eastern Province of Saudi Arabia. It is developing ballistic missiles that could threaten its neighbors and—especially if they are capable of carrying nuclear warheads—could provoke an arms race in the region. Iranian authorities detain and jail foreigners, including Americans, on fabricated charges. And the Iranian government oppresses its own people by coercing them into obeying strict religious rules, limiting their political choices, and abusing and imprisoning journalists.

This list of misdeeds served as the pretext for the Trump administration’s unilateral withdrawal in May 2018 from the Joint Comprehensive Plan of Action (JCPOA)—the Iran nuclear deal—and for the reimposition of US sanctions on Iran. The withdrawal made emphatically clear that rollback—coercively reversing any Iranian gains in regional power and influence rather than just containing them, with an eye ultimately toward regime change in Tehran—is the policy that the administration now embraces. It wants to force Iran to curtail its ballistic missile development and its provocations in Iraq, Syria, and Yemen—none of which the JCPOA addresses—as well its nuclear program. Strongly supporting this hard-line position is Saudi Arabia under its de facto leader, Crown Prince Mohammad bin Salman, which has become the United States’ main Arab partner in the Middle East.

Yet Iran had continued to observe the JCPOA’s limits on its nuclear program until recently, when it declared its intention to breach the 3.67 percent uranium enrichment limit stipulated by the agreement and said that it…