War of the Succession of Flanders and Hainault

The War of the Flemish Succession was a series of feudal conflicts in the mid-thirteenth century between the children of Margaret II, Countess of Flanders. They concerned the succession to the two countries, the first a fief of the King of France and the latter of the King of Germany.

When Baldwin IX, Count of Flanders and Hainault, left on the Fourth Crusade in 1202, he left his western domains under his eldest daughter Joanna. Joanna inherited the counties on Baldwin's death and, despite two marriages, died without heirs in 1244. She was succeeded by her younger sister, the aforementioned Margaret.

Margaret's first marriage, to Bouchard of Avesnes, was broken in 1221 per orders from Joanna and the excommunication of Bouchard. By Bouchard, however, she had already had three children, including John I of Avesnes. Nevertheless, in 1223, Margaret remarried with William II of Dampierre (d.1231), who likewise gave three offspring, including William III and Guy of Dampierre.

The rights to Margaret's inheritance between the sons of Avesnes and those of Dampierre were the cause of the conflicts known as the "war of the succession of Flanders and Hainault."

The first conflict opened with Margaret's succession in 1244. John I of Avesnes and William of Dampierre, half brothers, fought between themselves until King Louis IX intervened in 1246. Louis gave Hainault (technically not his to give) to John I of Avesnes and Flanders (indeed his vassal) to William of Dampierre. Margaret, in light of this judgement, gave the government of Flanders over to William of Dampierre in 1247. She did not however relinquish her governance of Hainault to John I of Avesnes.

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