Hyojong of Joseon vs William IX of Hesse-Kassel

King Hyojong initiated a plan to invade Qing China to avenge the humiliation of the 1636 surrender. He expanded the army, built fortifications, and stockpiled weapons. The plan was never executed due to Qing power and lack of allies.

Hyojong strengthened the Joseon military by reorganizing the army, improving artillery, and fortifying northern borders. He also promoted the use of matchlock muskets and trained a standing army, preparing for a potential war with Qing.

King Hyojong died suddenly at age 40, possibly from illness or poisoning. His death ended the Northern Expedition plan. His successor Hyeonjong was young, leading to a power vacuum and intensified factional strife.

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.