Some years earlier William had supported the exiled Count Herbert of Maine when Geoffrey Martel invaded the province and captured its main town Le Mans. As part of the pact William and Herbert agreed that if Herbert died without an heir the province could be claimed by William. William's eldest son Robert Curthose was betrothed to Herbert's daughter (Margaret?) but she died before they could be married. When Herbert died William claimed Maine in the name of his son and invaded. Robert was made Count of Maine when the province was captured. ¹

During the winter of 1078/9 William the Conqueror laid siege to Gerberoy Castle which was the stronghold of his son Robert who had rebelled against him. ¹

In a battle outside Gerberoy Castle William the Conqueror was unseated from his horse. The person responsible was his son Robert. When Robert discovered he had unhorsed and injured his father he assisted William to remount and leave the battlefield. This was a humiliating defeat for William who had been seen to be invincible. ¹

Possibly with the the help of Matilda, his mother, the rebellious Robert was reconciled with his father William.

Many Norman barons held land both in England and Normandy. With two opposing lords, William in England and Robert in Normandy, the barons were finding it difficult to know who to support. A revolt led by Odo sprung up in England with the aim of removing William from the throne. Odo's revolt in Kent and Sussex was supported by barons across the country. Roger Bigod from Norwich and Geoffrey of Coutances and Robert Mowbray from Bristol supported Odo. In Worcestershire Roger de Lacy captured Hereford and attacked Worcester. In the south-east Roger Montgomery at Arundel Robert of Mortain at Pevensey and Gilbert de Clare at Tonbridge also prepared to fight the King. Robert of Belleme, a Norman baron, who was able to bring support from Normandy. Robert also controlled castles in the Welsh Marches where the revolt also took place.

William Rufus lay siege to Pevensey Castle where Odo had taken shelter with Robert of Mortain. The siege lasted for six weeks. Robert, the Duke of Normandy, sent a force to support the rebels at Pevensey but they were unable to land because the King had made sure the ports were well guarded. Robert admitted defeat and withdrew his support for the rebels. Odo had little choice, other than that to starve, and surrendered to the King. Odo agreed to go to Rochester where he would convince the rebels to accept William Rufus as the rightful King of England.

Odo was accompanied to Rochester Castle by an escort but When they reached the castle the rebels captured the escort and refused to accept William Rufus as their King. Again William called for the people of England to support him against the rebels and together they lay siege to the castle. Odo surrendered when it was agreed that those in the castle would have their lives spared if the they came out. Odo and the rebels were allowed to leave but their lands in England were taken from them. Odo went into exiled in Normandy.

King William II took an army into Normandy and attacked the army of his elder brother Robert Curthose, the Duke. William claimed some of Robert's lands after the brothers agreed to peace. One term of the agreement was that Edgar the Atheling should be expelled from Normandy as his potential claim to the English throne was a threat to William.

Robert of Normandy became under pressure from William Rufus who laid claim to Normandy. William was gaining support from some Norman barons and Robert took the opportunity to leave Normandy to answer Pope Urban II's call for a Crusade. Robert agreed that William could lease Normandy for three years for a sum of 10,000 marks. This money would help him fund the expedition.

In late 1096, Stephen of Blois, his brother-in-law Robert Curthose, duke of Normandy, along with his cousin Robert, count of Flanders set out for the Holy Land. They reached Constantinople in May of 1097 and were warmly welcomed by Emporer Alexis. They then joined the main party of Crusaders and helped capture the city of Nicea.

Ranulf Flambard escaped from the Tower of London and fled to Normandy. There he joined Robert II of Normandy who had just returned from the Crusades. Flambard and Robert planned to take the English throne away from his younger brother Henry I.

Robert Duke of Normandy landed at Portsmouth with an army and marched up to Alton on the way to London. Here he and King Henry I signed the Treaty of Alton where Robert gave up his claim to the throne of England in return for 3 thousand marks a year. The treaty also ensured that Robert's supporters would not be punished.

Robert of Normandy visited King Henry and told him that he did not need to pay Normandy the three thousand marks a year which he should have done bound by Treaty of Alton. ¹

Cattle as well as corn and fruit crops did badly this year. ¹

King Henry I entered Normandy to take power from this brother Robert whose incapacity to manage the affairs of the region could have had grave consequences. Robert fought back forcing Henry to return to England but not before Henry had gained Caen and Bayeux.

King Henry I attacked his brother Robert at the battle of Tinchebrai. This time with a much larger force Henry defeated and captured Robert along with William, the Count of Mortain. Henry locked Robert in Cardiff castle where he remained until he died in 1135. Also captured was Edgar the Atheling who had sided with Robert. Edgar was released as King Henry did not think he was a threat.

Robert Curthose, William the Conqueror's eldest son, died in captivity in Cardiff Castle where he had been locked up since being defeated by his brother in 1106. Robert was buried in Gloucester Cathedral where there is an effigy of him still.