These tribes were subjugated by Cæsar, and the Veneti almost exterminated by him. Under the Romans, the culture and the language of the conquerors were rapidly assimilated. Christianity took root at Rennes and Nantes and Vannes, but almost nothing was done for the rural population, which probably still spoke its agglutinative tongue akin to the modern Basque. The stately bishops of these Gallo-Roman cities confined themselves to ministering to the cultured residents within their walls, and in villas scattered along the coast. The Gallo-Roman population had dwindled to an incredible extent, under the exactions of the imperial tax-gatherers, so that all the country residences fell into ruin, and the impoverished Gallo-Romans withdrew into the towns. But early—very early in the 5th century, fleets of British settlers came over, flying from the swords of Picts and Scots, and occupied the land about the mouth of the Loire. By 469 they were so numerous as to be able to send a contingent of twelve thousand men to the assistance of the Romans against the Visigoths.
As a consequence of the Saxon invasion of Britain the immigration grew, and the dispossessed islanders sought and found a new home in the Armorican peninsula, where they established themselves under their own princes, with their own institutions, civil and ecclesiastical, and their own tongue. Thenceforth Armorica ceased to be so called, and received the name of Lesser Britain, and the current language became British, identical with that now spoken in Wales, and spoken till the 17th century in Cornwall as well. Contact with France along the East has gradually thrust back the Breton language, but it is still spoken from Guingamp, in a slanting line to the mouth of the Loire. Two British kingdoms were formed, Domnonia and Cornubia; the former included the Côtes-du-Nord and Finistère above the river Elorn, and Cornubia or Cornouaille was the district below that river, the basin between the Monts d'Arrée and the Montagnes Noires, and stretched to the river Ellé at Quimperlé. All the department of Morbihan was the Bro-Weroc, a county, but the British chief did not call himself its king, probably because the colonists did not get hold of Vannes, the capital, which they enveloped but left unmolested.