President Donald Trump has tweeted a couple things related to America’s response if Iran retaliates for the US killing of the Islamic Revolutionary Guard Corps (IRGC) Quds Force Commander Qasem Soleimani. The subject’s seriousness warrants clarification and correction.

He wrote:

But is Trump really supporting a disproportionate response against Iran? US military responses must be, and have been during the Trump administration, proportionate.

It seems pretty clear the president intended to signal that Iran would be foolish to harm Americans or our interests and that his response would be more damaging to Iran than whatever Iran could do to us. In other words, it would not be tit-for-tat. That’s a perfectly fine and, in fact, good intent. President Trump seems to appreciate the value of hard power and, importantly, the superiority of our hard power over other nations. His appreciation of hard power and his willingness to use it has created some interesting diplomatic possibilities.   

But in warfare “proportionality” does not mean tit-for-tat (i.e., you hit our drone, so we hit yours). You don’t have to be a military strategist to see how an application of that misunderstanding of proportionality would lead us to a long war without an objective in view. It would be foolish.

To its credit, the Trump administration has avoided this kind of proportionality. Iran downed a US drone in June 2019, and when President Trump was given options to respond so that Iran didn’t down another or hit a military base, he went with a cyberattack. According to reports, his other options would have resulted in Iranian loss of life. Right or not, Trump seems to have assessed that taking Iranian life was excessive relative to his more immediate goal, compelling Iran to stop downing US drones. Perhaps now with hindsight we can conclude the cyberattack may have prevented Iran from carrying out a similar act of aggression, but it was insufficient to prevent Iran from acting in other harmful ways. Iran has not stopped other attempts to harm US assets, and the militias it backs have been trying to harm US and collation forces. Particularly, Iran was behind the Iraqi militia attack that killed a US Department of Defense contractor. Still, Trump’s thinking was in line with the just war tradition’s concept of proportionality.

Generally, according to just war tradition, when leaders consider going to war, they should weigh the desired good the war could achieve against the harm the war would cause. This is called jus ad bellum proportionality. Once the war begins, considerations of proportionality continue, but those require weighing potential military gains relative to the suffering military action causes. This is called jus in bello proportionality.

President Trump is wrong to state his willingness to seek disproportionality. Thankfully, thus far his actions are in line with the principles of proportionality.

Which brings us to Trump’s next problematic threat. The president threatened to hit Iranian cultural sites:

Targeting cultural sites would be morally wrong, illegal, and practically counterproductive.

Attacking cultural sites is wrong because of proportionality and discrimination. Unless the Iranian regime has hidden military assets within cultural sites, hitting them would not serve a military purpose. Even if one could hypothetically argue that targeting these sites could cause the Iranians to sue for peace—they surely would not—other targets, if destroyed, would serve US interests in pursuit of our military and political objectives and would cause less suffering for the Iranian people. Thus, we should target those.

If the US did decide to respond militarily to the Iranian regime’s next move, we should do so in a way that helped us. That would entail destroying the regime’s ability to carry out a strategic attack. In other words, why waste munitions on a museum when we can hit a missile production facility?

Targeting cultural sites for the sole purpose of retribution would also be illegal. US law (the War Crimes Act, 18 U.S.C. Section 2441), forbids certain crimes committed in war and partially defines them by referring to the Geneva Conventions, which the United States has signed and ratified. The Geneva Conventions prohibits the destruction of civilian property of cultural significance unless militarily necessary.

Last, such attacks would be strategically counterproductive. Hitting a cultural site would likely push Iranians on the fence to side with the regime and against the United States and energize those already rallying around the regime. This is the opposite of what the US wants, which is to support the Iranian people against their greatest abuser—the Iranian regime. Our traditional allies would also almost certainly condemn the attack, and the United States would need their support in the event of a broader, bigger war with Iran than the relatively restrained one now.

For those reasons, even threatening to hit cultural sites is profoundly unhelpful. Some have tried to argue that Trump’s threat to cultural sites helps deterrence, but that’s doubtful. Deterrence relies on the ability and will to carry out threats. It is unbelievable that the US military would carry out such brazenly immoral and illegal acts. Therefore, the threats aren’t credible, and consequently, neither is the attempt at deterrence.

After many decades of more idealistic foreign policy based on faulty assumptions about human nature and what soft power can accomplish, whose supporters often defend in moralistic prose, the Trump era is forcing a return to a more realistic approach. But a more realistic foreign policy that fiercely prioritizes the protection of America and our people is not any less concerned with morality. Indeed, it rightly prizes justice above all.