Danjong of Joseon vs John of Brienne

Danjong became king of Joseon at age 12 following the death of his father, King Munjong. His youth made him vulnerable to power struggles among the court, particularly from his uncle, Grand Prince Suyang (later Sejo).

Danjong was forced to abdicate by his uncle, Grand Prince Suyang, who seized the throne as King Sejo. Danjong was demoted to the rank of prince and placed under house arrest, ending his brief reign.

Six loyalist ministers (Sayuksin) who plotted to restore Danjong to the throne were discovered and executed by Sejo. The failed plot intensified Sejo's persecution of Danjong's supporters.

Danjong was murdered on Sejo's orders, likely by poisoning or forced suicide, at age 16. His death eliminated the last threat to Sejo's rule and solidified the usurper's hold on the throne.

John of Brienne was elected King of Jerusalem by the Haute Cour, marrying Maria of Montferrat, the heiress. He became king at a time when the kingdom was reduced to the coastal city of Acre and faced threats from the Ayyubids.

John of Brienne led the crusader forces in the Fifth Crusade, besieging the Egyptian city of Damietta. After a long siege, the city fell in 1219, but the crusaders failed to capitalize on the victory due to internal divisions.

John of Brienne negotiated with Ayyubid Sultan al-Kamil, who offered to return Jerusalem in exchange for the crusaders leaving Egypt. John refused, influenced by the papal legate Pelagius, leading to the eventual failure of the Fifth Crusade.

John of Brienne was elected Latin Emperor of Constantinople, ruling as regent for the young Baldwin II. He brought military experience to the beleaguered empire, which was threatened by the Byzantine Empire of Nicaea and the Second Bulgarian Empire.

John of Brienne successfully defended Constantinople against a siege by John III Vatatzes of Nicaea and Ivan Asen II of Bulgaria. His leadership preserved the Latin Empire for another generation.