The War of English Succession was a war over the throne of England in 1066.
The causes of this succession crisis in England were quite simply greed. William the Bastard of Normandy claimed he had been verbally promised the throne of England. Tostig Godwinson, the King's brother, contested his brother's right to inherit. Harald Hardruler of Norway made no pretenses about his invasion at all; his claim to the English throne was simply force.
Tostig Kinslayer, exiled brother to king Harold Godwinson, had begun raiding the coasts with the aid of a Flemish fleet, later joined by ships from Orkney. Tostig was driven off by the Earl of Northumbria but was able to retreat to Scotland, where he spent the summer recruiting additional followers.
Tostig, however, was not the only contestant to the English throne. William the Bastard of Normandy, intending to secure his own claim to the throne, had assembled a large invasion force including contingents from Flanders and Brittany. The fleet was launched on August the 12th, despite unfavourable weather. Unfortunately for the Normans, they were intercepted by the powerful English fleet. Scattered by rough weather, the Norman fleet suffered many casualties, although they inflicted quite a few of their own.
Harold scarcely had time to revel in his victory, however. Only a few precious weeks later, the forces of King Harald III of Norway, composed of over 15,000 and 200 ships, struck in the north. Joined by Tostig, who had decided that his brother's lands would be his if his brothers crown could not be, the Norwegian army proved a far more serious threat to Harold's reign. The first resistance Harald's forces received was at Scarborough; following the burning of this town much of Northumbria surrendered. News of the raiders reached the Earls of Mercia and Northumbria, who met Harald in the battle of Fulford. Harald's forces won the day and captured the city of York.In the meantime, Harold had hastily gathered his forces and rapidly marched north. His reckless haste would prove his downfall. The two armies met at Stamford bridge, where the Norse held the day. In the midst of the combat Tostig Godwinson found him face to face with his brother. Not recognizing him, he cut him down. With their king dead the English scattered.
Harald's rule in England was far from secure. Tostig proved highly unpopular, which only exasperated rebellions by the Anglo-Saxons.
Upon Harald's death in 1083, Olaf III succeeded him as ruler of England and Norway. Tostig Kinslayer attempted revolt, intending to claim his brother's crown, but was abandoned by the Anglo-Saxon nobles and killed at the Battle of Wessex. In reaction to this, in 1091 Olaf introduced the policy of allowing the Anglo-Saxons to select a Jarl to rule over their land in his name while he was absent; this was a non-hereditary position. His more positive relationship with the church and introduction of the guild system proved popular.England in this time began to experience an economic boom. Many thanes and earls, having learned from the failed rebellions of their kinsmen, began investing their wealth in building stone fortifications.