Big anthropological surveys are feats of cultural diplomacy, requiring years of negotiation and persuasion. And when regular diplomacy breaks down because of hostility or instability, museums feel the impact.

We were reminded of this last spring, when Asia Society’s exhibition of Buddhist art from Pakistan was delayed for six months. And now again as the Metropolitan Museum of Art’s “Byzantium and Islam: Age of Transition” opens without some important loans from Egypt.

Rest assured, pieces from Jordan, Greece and Georgia made the trip and are more than enough to tell the story of the Byzantine Empire in the Eastern Mediterranean, from Syria through Egypt and across North Africa, as it made contact with (and lost ground to) the emerging Islamic world between the seventh and ninth centuries.

The Met’s show concludes a series of Byzantine art blockbusters that includes “The Glory of Byzantium” in 1997 and “Byzantium: Faith and Power” in 2004, both also organized by the museum’s curator of Byzantine art, Helen C. Evans. (The Met’s first major exhibition on Byzantium was “The Age of Spirituality” in 1977.) But “Byzantium and Islam” differs substantially from its dazzling and opulent predecessors.