Wilson is a writer based in the District.

The ancient statue of a winged bull with a human face in Nimrud, Iraq. Last week, the Islamic State militant group destroyed the site.(Karim Sahib/AFP via Getty Images)

Last week, the Islamic State bulldozed Nimrud, the 7th-century B.C. capital of the neo-Assyrian Empire, then the most powerful nation-state on Earth.* Videos showed militants defacing and destroying massive statues of winged bulls and lions. On Saturday, they took aim at another ancient site, Hatra, a 2,000-year-old city built by the Parthians. It was the capital of the first Arab kingdom.

Human history is under assault in Iraq, and some of the irreparable damage is our fault. More than a decade of war in Iraq has taken an incredible toll on our cultural heritage, both in terms of priceless works of art and sites that hold evidence of some of the earliest civilizations in human history.

It didn’t have to be this way. Before the invasion, the U.S. military actively planned to avoid harming some of the most important archaeological sites in Iraq. In October 2001, the Pentagon contacted some of the most prominent Afghanistan and Iraq archaeology experts in the United States to compile a list of sites the military should protect in both countries.

Nimrud was on the list. So was the Iraq Museum.

Despite that planning, the U.S. military did its own damage: In ancient Babylon, an American-built helipad destroyed several nearby buildings.

And in the fog of war, many young American soldiers quite understandably prioritized their own safety and that of the population over what they saw as little more than clay tablets.

In the days after the U.S.-led invasion, American soldiers stood by and watched as looters stormed the Iraq Museum and ransacked its vast collections. The looters carted off an estimated 15,000 items — among them some of the best-known artifacts left behind by civilizations long since lost to history. (Donny George, the curator, saved thousands of other items by hiding them in the museum’s underground vaults, literally cementing them into the walls.) The thieves knew what they were looking for, which suggested that they had been given orders by wealthy collectors.

When the museum reopened last month, only about 9,000 of those items were recovered.

Senior U.S. government officials did not take the looting seriously. In a news conference in 2003, then-Defense Secretary Donald Rumsfeld joked about it: “The images you are seeing on television you are seeing over, and over, and over, and it’s the same picture of some person walking out of some building with a vase, and you see it 20 times, and you think, ‘My goodness, were there that many vases? Is it possible that there were that many vases in the whole country?'” Rumsfeld asked. Reporters in the room laughed.

But those vases were bringing in millions of dollars to fund the insurgency that targeted American soldiers, according to Matthew Bogdanos, a Marine colonel and assistant district attorney in New York City who investigated the illegal antiquities trade.

“The Taliban learned to finance their terror through opium,” he said. “They don’t have opium in the Middle East. What they do have is antiquities. It’s the cash crop.”

Wealthy collectors in Europe, Asia and even the United States used the Iraq war to build their own private museums — and their money helped fund both the insurgency that claimed the lives of so many American soldiers then and the Islamic State now.

Bogdanos’s investigation traced tens of millions of dollars from the sale of stolen artifacts to the coffers of the Iraqi insurgency. When I spoke to him in 2007, while reporting a story on the looted Iraqi artifacts for National Journal, he was unequivocal: Collectors in Europe, Japan and, yes, the United States “buy the weapons and bombs that are killing U.S. military personnel.”

Interpol, the international police organization based in France, even set up a special unit in its stolen-art department dedicated to finding and repatriating artifacts stolen from Iraq.

So far, it hasn’t done much good. The Antiquities Coalition, a group that battles cultural racketeering and advocates stronger laws against trafficking, says it has seen an uptick in the number of artifacts from Iraq and Syria for sale on the collectors market in the past few months. Both the U.N. Security Council and the Financial Action Task Force, an international body tasked with countering terrorist financing and money laundering, have issued findings citing the Islamic State’s role in the antiquities trade.

“It really is a massive illegal industry, especially in Syria. It’s organized, and ISIS is taking a very business-like approach to it,” said Tess Davis, the coalition’s executive director, using an acronym for the Islamic State. “The only people to profit from this are criminals, are terrorists and the very unscrupulous collectors.”

Even if the stolen artifacts are recovered, they will be far less valuable to the archaeologists and anthropologists who study them. By removing them, looters rob objects of their provenance — the information about where an object was found, in what stratum of soil and in what relation to other objects, information that is as valuable, in many cases, as the item itself.

The mass looting of cultural heritage is nothing new. Davis pointed to Nazi looting of Jewish heritage in Warsaw, the Khmer Rouge in Cambodia and the Taliban’s destruction of the Bamian Buddhas in Afghanistan. But what is new is the way art dealers and looters are making it possible for terrorist organizations to survive and thrive. “It’s not just about rocks and pots and even ancient palaces and ruins,” she said. “This is really a threat to the people of Iraq.”

And protecting Iraq’s cultural heritage was incumbent on the United States, too. The Pentagon failed to make adequate plans, and greedy collectors helped fund those who would target American troops.

In 2003, Army Col. Christopher Varhola, who helped compile the list of cultural sites to protect, sent an e-mail to one of the professors he had consulted after he inspected the looting of the Iraq Museum: “We have left our mark on history,” he wrote. “But so too did the Mongols and the Vandals. I do not understand why I expected us to be any different.”

* Correction: An earlier version of this post incorrectly stated the date that Nimrud was the capital of the Neo Assyrian empire.