De Administrandis Marcis: The 10th-Century Frontier with Islam seen from Barcelona and Byzantium

In the 950s and 960s Borrell II, Count of Barcelona and several other territories, faced the forces of Islam across an open frontier to his south and west, which he spent most of his long rule (945-93) attempting to manage. During that time Emperor Constantine VII Porphyrogenitos was also seeking, with episodic success, to manage another long frontier with Islam. More than contemporaneity and Muslim enemies makes these rulers comparable, despite their very different standings: both their fathers retired to monastic life, they both had to share initial power with siblings and both sent embassies to the same rulers of Córdoba and Rome. More importantly, while some of their approaches to their problems were extremely different, particularly in the military sphere, they both made extensive use of carefully-engineered versions of the past to justify, legitimate and build upon their status and power. This paper will use Constantine's De Administrando Imperio and De Ceremoniis, with a suitably critical eye, in comparison with Borrell's equally but differently complex charter corpus, to deepen these comparisons and ask what we can say about their management and description of their frontiers that brings us closer to what the tenth-century frontier was for its contemporaries.