A part of ancient Armorica, the area was conquered by Julius Caesar in the Gallic Wars and became part of the province of Lugdunensis (see Gaul). It received its modern name when it was settled (c.500) by Britons whom the Anglo-Saxons had driven from Britain. Breton history is a long struggle for independence—first from the Franks (5th–9th cent.), then from the dukes of Normandy and the counts of Anjou (10th–12th cent.), and finally from England and France.
In 1196, Arthur I, an Angevin, was acknowledged as duke. King John of England, who presumably murdered him (1203), failed to obtain the duchy, which passed to Arthur's brother-in-law, Peter I (Peter Mauclerc). The extinction of his direct line led to the War of the Breton Succession (1341–65), a part of the Hundred Years War (1337–1453). With the end of the Breton war, the dukedom was won by the house of Montfort. The dukes of Montfort tried to secure Brittany's neutrality between France and Britain during the remainder of the Hundred Years War.
The unsuccessful rebellion of Duke Francis II against the French crown led to the absorption of Brittany into France after the accession of his daughter, Anne of Brittany, in 1488. King Francis I formally incorporated the duchy into France in 1532. Brittany's provincial parlement met at Rennes, and its provincial assembly remained powerful until the French Revolution.
The 16th and 17th cent. were generally peaceful in Brittany, but the region, never reconciled to centralized rule, became one of the early centers of revolt in 1789. However, its staunch Catholicism and conservatism soon transformed it into an anti-Revolutionary stronghold; the Chouans (anti-Revolutionary peasants) were never fully subdued, and in S Brittany and the neighboring Vendée the Revolutionary government resorted to ruthless reprisals.
Breton nationalism grew in the 19th cent. and was fueled by the anticlericalism of the Third Republic. The Breton autonomists, long successfully repressed by the French government, nevertheless resisted German bids for collaboration in World War II. During the 1970s, Breton nationalists once again protested the French repression of Breton culture. Groups such as the Breton Revolutionary army and the Movement of National Liberation by Socialism committed sporadic acts of violence, such as the exploding of a bomb in the palace of Versailles in June, 1978.