Duke of Normandy as the reign of William II (1035–87), the ruler of Normandy could style himself "prince and duke, count of Normandy" as if unsure what his title should be. The literal Latin equivalent of "Duke of Normandy", "dux Normanniae", was in use by 1066, but it did not supplant "dux Normannorum" until the Angevin period (1144–1204), at a time when Norman identity was fading. Richard I experimented with the title "marquis" ("marchio") as early as 966, when it was also used in a diploma of King Lothair. Richard II occasionally used it, but he seems to have preferred the title duke.
William, Duke of Jülich-Cleves-Berg William, Duke of Jülich-Cleves-Berg William of Jülich-Cleves-Berge (William I of Cleves, William V of Jülich-Berg) (; 28 July 1516 – 5 January 1592) was a Duke of Jülich-Cleves-Berg (1539–1592). William was born in and died in Düsseldorf. He was the only son of John III, Duke of Jülich-Cleves-Berg, and Maria, Duchess of Jülich-Berg. William took over rule of his father's estates (the Duchy of Cleves and the County of Mark) upon his death in 1539. Despite his mother having lived until 1543, William also became the Duke of Berg and Jülich and the Count of Ravensberg. From 1538 to 1543,