William IV received about half of the territory, with Kassel as his capital. Hesse-Kassel expanded in 1604 when Maurice, Landgrave of Hesse-Kassel inherited the Landgraviate of Hesse-Marburg from his childless uncle, Louis IV, Landgrave of Hesse-Marburg (1537–1604). Thirty Years' War
William is a male given name of Germanic origin. It became very popular in the English language after the Norman conquest of England in 1066,  and remained so throughout the Middle Ages and into the modern era.