Claim: The County of Nantes, which served as a march against the Bretons of the Vannetais, finally fell to the Bretons and the title became a subsidiary title of the Breton rulers, which figured prominently in the history of the Duchy, in the mid-ninth century.
Evidence: Their county served as a march against the Bretons of the Vannetais. In the mid-ninth century, the county finally fell to the Bretons and the title became a subsidiary title of the Breton rulers. The control of the title by the Breton Dukes figured prominently in the history of the Duchy.