In deciding to eliminate General Suleimani, Mr. Trump and his team argue they were acting in self-defense to thwart imminent attacks on Americans in Iraq and the region. This may be true, as General Suleimani was a ruthless murderer and terrorist with much American blood on his hands. Unfortunately, it’s hard to place confidence in the representations of an administration that lies almost daily about matters large and small and, even in this critical instance, failed to brief, much less consult, bipartisan leaders in Congress.

Second, even if the killing of General Suleimani is justified by self-defense, it doesn’t make it strategically wise. Given the demonstrably haphazard and shortsighted nature of the Trump administration’s national security decision-making process (including calling off strikes against Iran 10 minutes before impact, inviting the Taliban to Camp David and abandoning the Kurds), it’s doubtful the administration spent much time gaming out the second and third order consequences of their action or preparing to protect American military and diplomatic personnel in the region.

To assess the fallout of killing General Suleimani, we must understand that the Iranian regime cannot survive internal dissent or sustain its powerful position in the region if it backs down from this provocation. For Iran’s supreme leader, Ayatollah Ali Khamenei, a strong response is essential. For the United States, the question is: What form will it take and how quickly will it come? One thing is clear: Americans are not safer, as Secretary of State Mike Pompeo argued on Fox News the morning after. Rather, American citizens are at greater risk of attack across a far wider battlefield than before.

Start with Iraq. The State Department has warned American citizens not to travel there. Iranian-backed militias have attacked United States and allied installations, and can continue to do so around the country. The government in Baghdad has declared the killing a violation of the terms of the American military presence in Iraq. We will face mounting pressure to withdraw our military and diplomatic personnel from the country. If we leave, the United States will suffer a major strategic defeat: Iran will justifiably claim victory, and the gains of the fight against ISIS will be lost as the terrorist group rebuilds.

There is no hope now to revive, much less strengthen, the Iran nuclear deal, and we must expect Iran will accelerate its efforts to revive its nuclear program without constraint.