Brittany was the only one of Henry II's continental dominions to be acquired by his own efforts, rather than by inheritance or marriage. The fact that Henry II had to acquire Brittany by his own efforts explains the disproportionately large amount of his own time and resources the king invested in this province.

Henry II did not, initially, plan to conquer Brittany. He would have been satisfied with recognition of his sovereignty by the native ruler. At the beginning of his reign, the king adopted the same policy towards Brittany as he did towards Wales, Scotland and later Ireland. That is, a native ruler was allowed to rule the province, subject only to his loyalty and possibly the payment of some form of tribute. In the case of Brittany, Henry II sponsored the young Duke Conan IV from as early as 1153. Even after the king seized the county of Nantes in 1158, his policy towards Conan as native ruler of the rest of Brittany remained unchanged.

From 1156, Angevin possession of the county of Nantes secured the borders of Brittany with the neighbouring provinces of Anjou and Poitou, which were already under Henry II's lordship. Further north, the king also pursued a policy of neutralising the potential threat to his lordship in Maine and Normandy posed by the marcher baronies of Vitré, Fougères and Combour. On these terms, Henry II was prepared to allow Conan IV to rule as duke of Brittany.