The shocking scenes of irreplaceable centuries-old treasures being smashed and toppled from their pedestals in a museum in Mosul — with the rabid acts of destruction proudly videotaped by fighters who call themselves the Islamic State — has provoked global outrage. But for Iraqis, who have seen decades of losses over centuries of intermittent war, this may be only the latest and most spectacular assault on the country’s cultural heritage.

Long before and since the 1990 invasion and occupation of Kuwait by Saddam Hussein’s troops and the American-led Persian Gulf War in 1991, which drove out the Iraqis and led to the most punishing postwar international sanctions the United Nations could impose, the treasures of Iraq have been in peril.

Situated on the sites of some of the world’s oldest civilizations — Sumerian, Assyrian, Babylonian and other pre-Arab-Muslim cultures — the area of ancient Mesopotamia saw battles between rival kingdoms and the depredations of invaders thousands of years ago. In the early Middle Ages, Christian Crusaders from Europe descended on the Middle East and destroyed Islamic sites and artifacts, a story well told in “Fields of Blood: Religion and the History of Violence,” a recent book by the scholar Karen Armstrong. Many thousands of people were slaughtered over centuries.

By the 19th century into the early 20th century, European explorers and colonial administrations were carrying away ancient treasures from Mesopotamia that became investments in private collections or museum trophies across Europe and North America. Throughout all of known history, the motivations of those who sacked settlements, sacred architecture and civilizations were not all religious. Often greed played a larger role, or the belief that artifacts needed to be removed to be preserved.

The most recent destruction and looting began after the 1991 war over Kuwait, when the sanctions imposed on Iraq pushed many middle-class families into poverty, and they began to sell treasures accumulated over years, including personal inherited antique jewelry as well as art and artifacts. By 1992, McGuire Gibson of the Oriental Institute at the University of Chicago, a leading archeological expert on ancient Mesopotamia, had cataloged many missing artifacts from Iraq.

“After the war, the selling started,” he told me in an interview in 1996. “Now, the stuff is just pouring out. If this continues, there won’t be an archeological site left that won’t be damaged.”

Soon gravediggers, smugglers, traders in illicit goods and criminal gangs worldwide got into the business of stripping Iraq of its treasures, from the small cylinder seals of metal or precious stones rolled on wet clay used to identify documents to huge pieces of statuary and monuments that experts say required large trucks to carry them off. Such large-scale thefts suggested at least semiofficial, perhaps Iraqi military, connivance. Monasteries and museums were looted, often with evidence of insider help. The National Museum in Baghdad was closed, and staff members showed me in 1998 some objects they had recovered and others they were planning to hide.

By 1998, when I was permitted to visit Hatra (the archeological site in the Mesopotamian Fertile Crescent, where some of the objects destroyed in February 2015 in Mosul have been unearthed in recent years), Iraqi and foreign experts told of industrial-scale destruction. In Hatra, thieves had lopped off the head of a king who ruled 18 centuries ago. In an ancient site at Khorsabad, the head of an Assyrian winged bull from the first century B.C. had been cut off and sawed into 11 pieces, apparently for easier shipping.

In this case, the robbers were apprehended as they tried to move their 1,500-pound trophy. They were arrested and at least six were executed, Iraqi officials said.

In the 1990s, thieves were arriving at important sites with guns, knockout drugs, cars with fake license plates and gangs of nomad laborers paid a small wage to do the digging, said Mouad Said, then the director-general of Iraq’s Department of Antiquities and Heritage in Baghdad. He added that the people in charge of the looting often brought lists of what to take, and appeared to have buyers abroad who had placed orders.

“The criminal world is so well organized that we can trace some routes from a Bedouin tent in the desert to one of the main dealers or collectors in England, the United States or Switzerland,” he said in an interview.

In the ruins of Hatra, one elderly guard with an old rifle was all the protection available when I visited the site in 1998. The antiquities department could not afford better security, and UN sanctions were inevitably blamed. Mouad Said had asked Unesco for a grant of $57,000 to buy two cars, a computer to create a database and photography equipment to document valuable pieces still in Iraq. He was turned down by Unesco, citing the restrictions imposed by UN sanctions.

Iraq had been guarding its antiquities and archeological sites well through much of the last century, experts say. That diligence was set back first by a seven-year war with Iran in the 1980s and events that followed. Plans to expand archeological work on the Hatra site were abandoned, Iraqis said.

Over the years, Iraqi forces have also done their share of looting in the neighborhood. The most famous case was the wholesale theft by Iraqi troops invading Kuwait in August 1990 of an estimated hundreds of millions of dollars’ worth of historic treasures, artwork and jewels from Kuwaiti museums and other collections as well as gold from the Kuwaiti central bank. Aircraft, private and commercial, were also seized by Saddam Hussein’s troops as they consolidated their seven-month occupation of the small neighboring country. When the Iraqis were forced to retreat, they set fire to hundreds of Kuwaiti oil facilities in a final act of destruction.

Though Iraq’s foreign minister at the time, Tariq Aziz, promised after the 1991 first Gulf War, which drove Iraqis out of Kuwait, that all stolen items would be returned, the promise was not kept. When the UN created a program allowing Iraq to export supervised amounts of oil to buy food and other civilian goods to alleviate shortages caused by international sanctions, part of the money to be earned by Iraq was earmarked by the UN for reparations to Kuwait.

Hundreds of pieces of art and archeological objects are still reported to be missing, however, and Iraq has not completed reparations payments. In December 2014, the current Iraqi government asked and received a two-year extension until 2016 of the deadline for its final payment. Iraq has already paid nearly $50 billion into the UN fund overseeing compensation for looting and damage inflicted during the occupation of Kuwait, according to a Reuters report.

In 2003, when the American-led second Gulf War broke out, which ultimately toppled Hussein and led to his arrest and hanging, attention was focused again on the looting of Iraqi treasures. In the chaos that followed Hussein’s overthrow, about 15,000 artifacts were reported looted from the National Museum of Iraq. About a third were later found and returned. But the museum remained closed for 12 years.

On Feb. 28 of this year — ahead of schedule, as a defiant response to the atrocities in Mosul — Iraq reopened the museum.

Many people, including journalists, think erroneously that the looting in 2003 was a new phenomenon and threat to Iraq’s cultural heritage. Sadly for the Iraqis, it was only another chapter in the slow-motion death of history in a unique land.

“Mesopotamia is not the cultural property of the Iraqi government,” Moaud Said said in 1998. “It is the property of humankind.”

Barbara Crossette

Barbara Crossette is the senior consulting editor and writer for PassBlue and the United Nations correspondent for The Nation. She is also a member of the Council on Foreign Relations. She has also contributed to the Oxford Handbook on the United Nations.

Previously, Crossette was the UN bureau chief for The New York Times from 1994 to 2001 and previously its chief correspondent in Southeast Asia and South Asia. She is the author of “So Close to Heaven: The Vanishing Buddhist Kingdoms of the Himalayas,” “The Great Hill Stations of Asia” and a Foreign Policy Association study, “India Changes Course,” in the Foreign Policy Association’s “Great Decisions 2015.”

Crossette won the George Polk award for her coverage in India of the assassination of Rajiv Gandhi in 1991 and the 2010 Shorenstein Prize for her writing on Asia.