- William III of Dampierre
William III (1224 –
6 June 1251 ) was the lord ofDampierre from 1231 andcount of Flanders from 1247 until his death. He was the son ofWilliam II of Dampierre andMargaret II of Flanders .Margaret inherited Flanders and Hainault in 1244 and immediately the
War of the Succession of Flanders and Hainault began between William and his brothers, the Dampierre claimants, and the children of Margaret's first marriage toBouchard of Avesnes . Margaret favoured William and declared him her heir. In 1246,Louis IX of France intervened to arbitrate the conflict and declared Flanders to William and Hainault toJohn I of Avesnes . Margaret officially invested William as count in 1247 and he is known, as count, as "Willem (or Guillaume) II."In November of that year, William married Beatrice, daughter of
Henry II, Duke of Brabant andMarie of Hohenstaufen . They had no children. Meanwhile the fight continued over Namur between the Dampierres and the Avesnes. On19 May 1250 , peace was signed. On 6 June the next year, William was assassinated at atournament inTrazegnies by a group of knights financed by Avesnes. The war began anew with Guy, William's younger brother, taking up Flanders and the Dampierre claim.
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