Hyojong of Joseon vs Petar I Karadjordjevic

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.

Petar I Karadjordjevic became King of Serbia following the May Coup that assassinated King Alexander Obrenovic. His accession restored the Karadjordjevic dynasty and was supported by the Serbian military and political establishment.

King Petar I led Serbia during the First and Second Balkan Wars. Serbia expanded its territory significantly, gaining Kosovo, Macedonia, and parts of Albania, establishing itself as a major regional power under his leadership.

King Petar I led Serbia through World War I after the Austro-Hungarian invasion. Despite the Serbian army's retreat through Albania in 1915, he remained with his troops and later returned to lead the country as part of the victorious Allies.

King Petar I became the first monarch of the Kingdom of Serbs, Croats and Slovenes (later Yugoslavia) after World War I. This unification of South Slavic peoples fulfilled his vision of a larger state, though he delegated governance to his son Alexander due to ill health.