Iran's cultural heritage is suddenly a topic of urgent global interest, after President Trump threatened to strike such sites if the country retaliates for the United States' killing of Gen. Qassem Soleimani last week.

In a series of tweets Saturday evening, Trump wrote that "if Iran strikes any Americans, or American assets," the U.S. has targeted 52 Iranian sites — "some at a very high level & important to Iran & the Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD."

Iran's foreign minister, Mohammad Javad Zarif, tweeted that targeting Iranian cultural sites would be a war crime.

On Monday, Defense Secretary Mark Esper indicated U.S. forces wouldn't carry out Trump's threat, saying, "We will follow the laws of armed conflict."

On Sunday, Secretary of State Mike Pompeo had appeared to walk back Trump's statements on ABC's This Week. "We'll behave lawfully, we'll behave inside the system, we always have and we always will," he said on Sunday morning.

Nonetheless, Trump doubled down on his threat. "They're allowed to kill our people. They're allowed to torture and maim our people. They're allowed to use roadside bombs and blow up our people," he told reporters on Sunday evening. "And we're not allowed to touch their cultural sites? It doesn't work that way."

The targeting of cultural properties by the U.S. is indeed not allowed. The U.S. is a signatory to the 1954 Hague Convention, which requires "refraining from any act of hostility" directed against cultural property.

The convention covers "movable or immovable property of great importance to the cultural heritage of every people, such as monuments of architecture, art or history, whether religious or secular; archaeological sites; groups of buildings which, as a whole, are of historical or artistic interest; works of art; manuscripts, books and other objects of artistic, historical or archaeological interest; as well as scientific collections and important collections of books or archives or of reproductions of the property defined above," as well as buildings and centers whose main purpose is to house such items.

It also bars using cultural sites "for purposes which are likely to expose it to destruction or damage in the event of armed conflict." That means signatory nations can't use such sites to house soldiers or weapons with the goal of shielding them from attack.

The convention permits immunity in "exceptional cases of unavoidable military necessity."

U.S. military policy agrees. The Department of Defense's Law of War manual mentions cultural property 625 times, repeatedly citing the Hague Convention. It also addresses the subject of military necessity: "Acts of hostility may be directed against cultural property, its immediate surroundings, or appliances in use for its protection when military necessity imperatively requires such acts."

Accordingly, the U.S. military educates its soldiers about their responsibilities not to target or destroy cultural property, and to help in its preservation, says Nancy Wilkie, president of the U.S. Committee of the Blue Shield. The organization is dedicated to the prevention of destruction and theft of cultural heritage.

The Pentagon has even distributed playing cards with photos of cultural sites in Afghanistan and elsewhere to remind troops to safeguard heritage sites and artifacts.

"Cultural sites and cultural objects that can provide sort of a baseline for recovering from strife, whether it's civil war or war against an external agent,'" says Wilkie, an archaeologist and the former president of the Archaeological Institute of America. "And so one way to demoralize the population is to destroy its cultural heritage."

As World War II was underway in 1943, then-Gen. Dwight D. Eisenhower issued an order to his commanders, demanding the protection of historical monuments:

"Today we are fighting in a country which has contributed a great deal to our cultural inheritance, a country rich in monuments which by their creation helped and now in their old age illustrate the growth of the civilization which is ours. We are bound to respect those monuments so far as war allows. "If we have to choose between destroying a famous building and sacrificing our own men, then our men's lives count infinitely more and the building must go. But the choice is not always so clear-cut as that. In many cases the monuments can be spared without any detriment to operational needs. Nothing can stand against the argument of military necessity. That is an accepted principle. But the phrase "military necessity" is sometimes used where it would be more truthful to speak of military convenience or even of personal convenience. I do not want it to cloak slackness or indifference."

The Hague Convention was developed after the war brought the destruction of important cultural sites such as the monastery at Monte Cassino, founded in 529 and bombed by the Allies in 1944.

The Department of Defense's Law of War manual quotes from Eisenhower's order and repeats some of its language in its current policy.

To aid the U.S. military in its obligations not to destroy important cultural heritage sites, the U.S. Committee of the Blue Shield has previously provided "no-strike lists" of such sites in countries including Iraq, Afghanistan and Libya.

The organization has not been able to compile such a list for Iran because it's been difficult for scholars to work there. "Iran is huge," Wilkie says, estimating that such a list would include 5,000-10,000 sites.

UNESCO has 22 cultural sites in Iran on its World Heritage List, from the ancient ruins of Persepolis to the historic bazaar complex in Tabriz.

Wilkie hopes that the U.S. military will stand by its policy to protect cultural sites, despite Trump's threats. Such places are important to local people as sites of honor or worship, she says, while others have worldwide significance.

"Culture is what we have," she says. "It reminds us of our past, and it unites us in our desire to preserve our sensibilities and sensitivities to cultural differences, and yet — to the fact that we're all human and we all share human values."

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