Sweyn Estridson and Harald Hardrada tried to establish an army to overthrow Magnus. But soon after Harald Hardrada made peace with Magnus, he had the viking mentality of always supporting the strongest side and Svein Estridson was the weakest and known for bad war luck. Magnus gave Harald Hardrada part in his kingdom in return for half of the share in Harald Hardradas Byzantine treasure. Svein did not like Harald Hardradas tradition for plundering and murder, because it was a way to gain unpopularity. Sweyn Estridson continued his struggle weakened.
An inheritance rebellion against William the Conqueror started with an ambush near Valognes on the Cotentin Peninsula, but the rebels failed. The noble rebels were Gui of Burgundy, Nigel of the Cotentin, Rannulf of the Bessin, Ralph Tesson of Thury, Grimoald of Plessis, and Haimo of Creully, they raised an army of 25000 men.
William the Conqueror escaped the ambush, he rode directly to King Henry's royal court in Poissy, and begged the king for help and claimed that a revolt against a loyal duke vassal was a revolt against the king himself.
The king of France, Henry raised an army of 10,000 men.