Stephen, King of England Robert of Gloucester rebelled against the King, starting the descent into civil war in England. An illegitimate son of Henry I and the half-brother of the Empress Matilda, Robert was one of the most powerful Anglo-Norman barons, controlling estates in Normandy as well as the Earldom of Gloucester. He was known for his qualities as a statesman, his military experience, and leadership ability. Robert had tried to convince Theobald to take the throne in 1135; he did not attend Stephen's first court in 1136 and it took several summons to convince him to attend court at Oxford later that year.
Norman conquest of England had moored for the winter south of the Humber in Lincolnshire, and drove them back to the north bank. Leaving Robert of Mortain in charge of Lincolnshire, he turned west and defeated the Mercian rebels in battle at Stafford. When the Danes attempted to return to Lincolnshire, the Norman forces there again drove them back across the Humber. William advanced into Northumbria, defeating an attempt to block his crossing of the swollen River Aire at Pontefract. The Danes fled at his approach, and he occupied York. He bought off the Danes, who agreed to leave England in the spring, and