On Thursday morning, the Syrian army took control of the Krak des Chevaliers, the famous 12th-century crusader castle in Homs province. On the heels of Wednesday’s victory in the southern village of Yabroud, the fort was the latest in a strong of government victories. It’s also the latest, and one of the most prominent, takeovers of a renowned heritage site in the country.

We spoke to Nada al-Hassan, head of the Arab States Unit at UNESCO’s World Heritage Center, to weigh in on the agency’s growing concerns and attempts to reach parties on all sides of the conflict.

Syria Deeply: How worried is UNESCO in the wake of this week’s events?

Nada al-Hassan: We are extremely worried because it’s still a battle zone, regardless of who’s controlling what. Our line is that of the appeal that the director-general made, with Ban Ki-Moon and [envoy to Syria] Lakhdar Brahimi, which is to call on all parties not to use cultural heritage sites for military purposes. The situation is worrying because there are more than 300 people living in the castle. It was a military fortress last used in the middle ages, it was a city inhabited by people. And now that it’s been taken back by the army, it’s in the hands of the military again.

All the military zones, all the cultural heritage fortresses, are being used for military purposes. Saint Simeon is a military camp now, a training camp. The citadel in Palmyra, the citadel in Aleppo, are occupied by the military. They are all in the middle of the battle and part of the strategic positions of each military.

SD: How important are Syria’s sites, in the global context?

Al-Hassan: The sites in Syria are extremely important: it’s a very valuable country for cultural heritage. You have six sites on the world heritage list and and a number of sites that aren’t but that are very important. The Krak des Chevaliers is a very important military construction. In the region it’s unique because it has dimensions that are well preserved in their entirety and that show the influence of the exchanges between the Byzantine crusaders and Islamic architecture. It’s singular in that it looks like a military fortress from the Middle Ages in Europe, but has lslamic influences and characteristics.

SD: Does one side seem to be less cautious around such sites than the other?

Al-Hassan: No, it’s war. War is not something where you worry about such things. The important thing for them is just to gain strategic dominance. Someplace like the Aleppo citadel is extremely important in terms of maintaining a strategic military presence in that city. If [a site] is at the center of a battle, no one will leave their position there just to preserve it.

SD: Has UNESCO appealed directly to each side?

Al-Hassan: All the appeals made have been made to all the parties in the conflict, and there have been at least 10 of them made. The director-general wrote to the U.N. Security Council, which issued a resolution that called on all parties not to [fight at the sites]. We’ve done press conferences, we’ve inscribed Syrian sites on the danger list. We’ve voiced all sorts of concerns.

SD: Illicit trafficking of artifacts has been a major problem for UNESCO since the beginning of the conflict. As the military situation deteriorates, is that getting worse?

Al-Hassan: Trafficking is getting much worse. On one hand the looting of museums has been more or less contained, because at the very beginning of the conflict, the Syrian government had an initiative to empty them of their content and put it in secure locations. But then in the case of the Raqqa Museum, everything was stolen from the secure location. Some artifacts were also taken [for safekeeping] by the Free Syrian Army, in the north.