This book began in Baltimore. But it was fostered in the remarkable scholarly repair of Dumbarton Oaks, and grew to maturity in the bracing clime of Cambridge, Massachusetts. It sprang, utterly unintended, from another research project, on diplomacy between the Carolingian and Byzantine empires. My intent had been a respite from the “powerful and sinister drama” of late antiquity, the social transformations of political power and its rituals which had formed the subject of Eternal Victory.

When I had about concluded the research for the diplomacy book, I sat down to write a brief chapter describing how two early medieval courts communicated. Within a few weeks it became clear that my prosopographical study of diplomats had uncovered much new evidence. A few months more of research, and I was back at Dumbarton Oaks to present a first sketch of my findings in an informal talk. I no longer remember everyone in the small group who attended that talk, but I do recall that my friends Alexander Kazhdan and David Jacoby were present. Both levied vigorous criticism of the sort that we all most enjoyed, even as they lent me further important evidence for my findings. Alexander, in particular, objected to detecting broad shifts in the infrastructure of Mediterranean shipping and transport on the basis of “only sixty pieces of evidence,” sixty instances of long-distance communication. We all laughed when I retorted that complaining about “only” sixty witnesses was rather unbecoming to a Byzantinist.