Guillaume the Conqueror (Ethelred the Pious)

Duke Guillaume (William) began life as "the Bastard" and ended it as "the Conqueror". Duke of Normandy from the age of eight, he waged a seemingly endless war to secure his inheritence and his conquests.

Early years
Guillaume's early life was the same as in OTL, the only difference being that he had no relation to the Nordic rulers of England. (His grandfather's sister Emma married into the English line in OTL; in this timeline she married a German prince, England still being a pagan country.)

In 1035 Guillaume succeeded to the ducal throne of Normandy at the age of eight. Strong guardians from Normandy and Brittany helped guard his position during his minority, and even after coming of age he dealt with a series of rebellions of his barons. By 1050 he was a seasoned fighter.

Guillaume's marriage to Matilda of Flanders in 1052 gave him an important ally. Between 1054 and 1060 he successfully defended Normandy against attacks from Anjou and the French king.

Expansion
Guillaume first looked outward in 1063 when he conquered the county of Maine from Anjou. The next year he sponsored a rebellion against his neighbor and relative, Duke Conan II of Brittany. Conan put down the rebellion successfully but was assassinated, possibly by Guillaume's agents, in 1066.

Conan's heir was his sister Hawise, but Guillaume claimed to be the legitimate ruler based on tenuous dynastic connections. No longer content to fight by proxy, Guillaume launched a massive invasion of Brittany by both land and sea. By the end of the year, Norman armies controlled the entire duchy, and the French king and clergy confirmed Guillaume as the new ruler by right of conquest.

Reforms and challenges
Guillaume's early years of insecurity had given him a great distaste for instability. He deprived Brittany's Celtic aristocracy of nearly all of their ancient lands, dividing them up among his Norman magnates. He ordered a meticulous survey of all the lands in Brittany, paving the way for an efficient medieval administration. He sponsored many building projects, most famously the Tour de Rennes in the Breton capital, for centuries a notorious prison for enemies of the state.

However, Guillaume's old enemies, the French King and the Duke of Anjou, continued to press from all sides, allied with Flanders' new Count, Robert. Guillaume's lands shrank somewhat by the time of his death in 1087, but he was still France's most powerful magnate, with feudal wealth greater than the king himself.

Guillaume feared disputes among his two eldest sons, so he made the difficult choice of re-dividing his territory at his death. Robert, the eldest, became Duke of Normandy, while Guillaume le Roux (Rufus) became Duke of Brittany. The youngest son, Henri, received a monetary inheritance.