The counts of Flanders and Hainaut who became the first Latin Emperors of Constantinople after the Fourth Crusade.
Baldwin IX, Count of Flanders and Hainaut, was one of the great princes of the Low Countries and a leader of the Fourth Crusade. When the crusade was diverted to attack Constantinople and stormed the city in 1204, the victorious Latins elected Baldwin as the first emperor of a new Latin Empire in place of the Byzantine one.
The new empire was a fragile Latin overlay on a hostile Greek world, surrounded by Byzantine successor states and the Bulgarians.
Baldwin I’s reign was short: in 1205 he was defeated and captured by the Bulgarian tsar Kaloyan at Adrianople and died in captivity. His brother Henry succeeded him and proved the most capable of the Latin emperors, holding the empire together against Greeks and Bulgarians alike through war and diplomacy until his death in 1216.
After Henry the crown passed by marriage to the House of Courtenay, and the Latin Empire slid into decline.
The Flanders-Hainaut emperors founded the Latin Empire that ruled Constantinople for half a century after 1204, one of the most striking consequences of the Fourth Crusade. Their rule deepened the schism between the Latin and Greek churches and left lasting bitterness in the Orthodox world.
The empire they created never recovered from Baldwin’s early loss, and in 1261 the Byzantines under the Palaiologoi retook Constantinople.