The Siege of Dol took place in September 1076 during a campaign against rebels based at Dol in Brittany.
After the failure of the Revolt of the Earls in England in 1075, the rebel Ralph de Gael, Earl of Norfolk, who already held land in Brittany, fled there where he joined a rebellion against the Duke Hoël II seized the castle at Dol, also menacing Normandy's western border. William the Conqueror, who had previously fought Ralph, took an army from England"King William now went over sea, and led his army to Brittany, and beset the castle of Dol; but the Bretons defended it, until the king came from France". "The city of Norwich, Chapter 5: Of the city in the Conqueror's time" to besiege Ralph in Dol in support of Hoël, but with winter approaching the siege was lifted when King Philip I of France and Fulk of Anjou intervened with a relieving army, inflicting William's first recorded military defeat. A peace settlement reached in 1077 at Orléans left Ralph in possession of Dol. The setback damaged William's prestige,Orderic Vitalis. William's army was forced to hastily retreat to England, losing many men and horses, and leaving behind expensive military equipment and treasures. although there is disagreement among historians who have argued that it hurt him in France and those who claimed it had little long-term political impact.
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