Edward the Confessor was the King of England until 1066.  After he died a man named Harold Godwinson claimed the throne.  His claim was backed by the Witenagemot.  The Witenagemot was an assembly of the most powerful English nobles.

When Edward was alive he did not rule independently.  Instead, he was influenced by his cousin William II of Normandy.  When Edward died William believed he was the rightful heir to the throne.  William took the crowning of Harold as King of England as a declaration of war against Normandy. Therefore, the Duke of Normandy led an army and invaded England in 1066 AD.

William’s army was around 20,000 strong.  His army was made up of Normans, Flemish, Bretons, and French from Paris.  I think there were even some Italians involved.  William promised to give land/title to all the lords that helped him in his invasion of England.  William even claimed that the pope at the time supported the Norman invasion.  On September 28th, 1066, William landed unopposed in England.

The English King, Harold II was expecting the invasion; however, he could not meet William in the south.  At the same time William landed, a Norwegian Viking army under the leadership of Harald Hardrada attacked from the north.  Harold led his army against the Vikings.  He defeated them during the Battle of Stamford Bridge.  He then rushed south to meet William.

The Battle of Hastings took place on 14 October 1066. It was the decisive Norman victory in the Norman Conquest of England, fought between the Norman army of Duke William II of Normandy and the English army of King Harold II.  The battle took place at Senlac Hill, approximately 6 miles northwest of Hastings, close to the present-day town of Battle, East Sussex.

Harold II was killed in the battle—legend has it that he was shot through the eye with an arrow. Although there was further English resistance, this battle is seen as the point at which William gained control of England, becoming its first Norman ruler, King William I.