Brittany, a region with an obscure early history and an identity in dispute between Britain and France, enters an unusually well-evidenced period in the ninth century when it was conquered, and then placed under native rulership, by the Frankish Carolingian emperors. Taking advantage of Carolingian weakness to expand territorially, the Breton polity outlasted dynastic violence and Viking attack and would eventually survive until 1532. The historiography of the period has blossomed since the 1980s. English- and French-language historians are in agreement that the creation of Brittany was a direct consequence of the rise and fall of the Carolingian empire, and an illustration of ‘the fundamental political and social changes that often occur on the periphery of dynamic and rapidly evolving societies’ (J.M.H. Smith). They differ, however, in that Francophones are inclined to emphasise the extension of Carolingian institutions to Brittany, while English historiography minimises the institutionalisation of politics, in Brittany and increasingly in the Carolingian empire as a whole. Regardless of these differences, Breton evidence gives a view of the interplay between the local and the supra-national in social organisation, legal practice, and Christian culture, the significance of which for the whole Carolingian world is increasingly recognised.