William IX of Hesse-Kassel

William IX became Landgrave of Hesse-Kassel upon the death of his father Frederick II. He inherited a wealthy state due to the lucrative practice of hiring Hessian soldiers to foreign powers, particularly Britain during the American Revolution.

As part of the Reichsdeputationshauptschluss, William IX was elevated to the title of Elector of Hesse-Kassel, becoming Elector William I. This increased his status within the Holy Roman Empire, though the title was largely symbolic.

After the Battle of Jena-Auerstedt, Napoleon's forces occupied Hesse-Kassel. William I fled to Denmark, leaving his territories under French control. He remained in exile until after Napoleon's defeat.

Following Napoleon's defeat at the Battle of Leipzig, William I returned to Hesse-Kassel and resumed his rule. He restored the old order, reversing many reforms introduced during the French occupation.