Henry I of France whose death Henry was left to deal with his rebel sibling. In 1032, he placated his brother by giving him the duchy of Burgundy which his father had given him in 1016. In an early strategic move, Henry came to the rescue of his very young nephew-in-law, the newly appointed Duke William of Normandy (who would go on to become William the Conqueror), to suppress a revolt by William's vassals. In 1047, Henry secured the dukedom for William in their decisive victory over the vassals at the Battle of Val-ès-Dunes near Caen; however, Henry would later support the barons against
William Ernest, Duke of Saxe-Weimar William Ernest, Duke of Saxe-Weimar William Ernest, Duke of Saxe-Weimar (19 October 1662 – 26 August 1728) was a duke of Saxe-Weimar. He was born in Weimar, the eldest son of Johann Ernst II, Duke of Saxe-Weimar and Princess Christine Elisabeth of Schleswig-Holstein-Sonderburg. When his father died in 1683, he succeeded him as duke; however, he was compelled to rule jointly with his younger brother Johann Ernst III. Because John Ernest III was alcoholic, William Ernest took full control of the government of the duchy and permitted John Ernest the nominal title of co-duke ("Mitherr") until his death in 1707.