This book began as a refinement of my doctoral dissertation which I defended at the University of Cambridge in April 1996. My thesis presents a distillation, in the form of four regional surveys, of the written and archaeological evidence pertaining to the Byzantine frontier in the northern Balkans in the period 971-1180. The refinement, I thought, should have a narrative structure, since no synthetic narrative political history of the northern Balkans exists in English for this period. I also decided to increase its chronological and geographical range to allow a cursory treatment of Bulgaria before the imposition of the ‘Byzantine Yoke’, and a fuller exploration of how the ‘yoke’ was cast off by Bulgarians, Vlachs, Serbs and others. In the end the refinement bears no resemblance whatever to the thesis. It takes as its central concern Byzantine responses, first to the migrations of nomadic peoples, and subsequently to the expansion of Latin Christendom. It also examines the changing conception of the frontier in Byzantine thought and literature through the Middle Byzantine Period.

In the course of writing the thesis and book I have enjoyed the support of a number of institutions. St John's College, Cambridge awarded me a Benefactors' Scholarship and travel funds sufficient to take me around Turkey and the Balkans more than once. The British Academy funded my Ph.D. I was honoured to be appointed to a British Academy Postdoctoral Fellowship, and privileged to hold this at Keble College, Oxford.