“A burdensome matter it is today to abandon the delicate and subtle customs of the Latin people, i.e. the Franks, and to return to the dullness of the old Armenians.” Thus wrote the Armenian archbishop Nerses, not without a hint of sarcasm, when defending his endeavour to unite the Armenian Church with the Roman in the late twelfth century. What this old dullness was is less clear but it seems that Latin customs had indeed become both desirable and powerful, for this ecumenical endeavour met with success and only a handful of years later something similar occured in the Balkans, when a newly founded Bulgarian empire submitted to the Roman Church as well. The rulers of these realms would not only profess their loyalty to the Roman Church but would also carry papal banners into battle and exchange letters with the pope. This study examines how these rulers used their relationships with the Papacy, as well as how the pope used his relationship with them. It is a study of ideas and of symbolic power, of how kingdoms and empires were imagined and expressed. It is a study of the new and the old, of two new power-centres emerging from the old peripheries of the crumbling Byzantine Empire, of leaders weaving together real and imagined histories with new influences in order to establish and profess their legitimate rule. This is a Doctoral Thesis in History of Ideas at Stockholm University, Sweden 2021