Meanwhile, the government-administered Smithsonian Institution, working with groups in the United States and the Middle East, began giving emergency training and technical support to Iraqi and Syrian preservationists. This has been crucial to the successful protection of sites and museums in northern Syria, among other places.

And in May 2016, President Barack Obama enacted bipartisan legislation to protect international heritage “at risk due to political instability, armed conflict, or natural or other disasters” — establishing for the first time a body within the executive branch to address the threat.

The American efforts coincided with bold new thinking in the international community. In 2016, recognizing that cultural destruction was directly related to ethnic cleansing, the International Committee of the Red Cross entered an agreement with Unesco, in which it pledged to help evacuate cultural objects “at imminent risk.” While the accord has not yet been tested in practice, it is significant because the I.C.R.C. is often on the ground on both sides of a conflict and has unparalleled access to sites.

With Unesco’s support, France and the United Arab Emirates established a $75 million fund to provide “safe havens” and other forms of protection for objects and monuments under threat of attack. The American investor and philanthropist Thomas Kaplan, who has given $1 million, is chairman of the fund.

Finally, in March, pushed by Unesco and the governments of France and Italy, the United Nations Security Council passed a resolution explicitly linking attacks on cultural heritage to terrorism and calling on member states to provide one another with “all necessary assistance” to prevent those attacks.

Over the past year, an independent, United States-based task force — sponsored by the J. Paul Getty Trust with support from the American Academy of Arts and Sciences — has been exploring ways to give teeth to these commitments. In a report to be released by the Getty Trust in December, the group draws on the Responsibility to Protect, or R2P, doctrine, adopted by the United Nations in 2005, which provides a basis for intervention to prevent humanitarian atrocities.

The movement to integrate cultural heritage into security policy has quickly gained support from several European governments and leading international institutions. In a landmark August 2016 decision against an extremist in Timbuktu, the International Criminal Court ruled the destruction of cultural heritage a war crime.