Two weeks ago, the famed Crusader castle Crac des Chevaliers, one of the irreplaceable Syrian heritage sites named to the 2014 World Monuments Watch, again found itself a target in the Syrian civil war.

This winter, the film "Monuments Men" told the story of how, over two years, with virtually no resources or support, a ragtag division of 345 volunteers from 17 countries working under the aegis of the Monuments, Fine Arts and Archives (MFAA) program rescued six million stolen artworks from Nazi depots, including...