King Gwangjong vs Li Yu

Gwangjong issued an edict freeing many slaves and reclassifying them as commoners. This measure aimed to undermine the economic base of powerful clans who relied on slave labor, while increasing the tax-paying population under direct royal control.

King Gwangjong initiated a systematic purge of powerful aristocratic clans that had dominated Goryeo politics. He ordered the execution or exile of many nobles, confiscated their lands, and freed thousands of slaves to weaken the old elite and strengthen royal authority.

Gwangjong established the gwageo civil service examination system in Goryeo, based on the Chinese Tang model. This reform allowed talented individuals from lower social classes to enter government service, reducing the power of hereditary aristocrats and creating a merit-based bureaucracy.

Gwangjong decreed that only the king could grant the right to wear purple robes, a symbol of high office. This edict stripped powerful nobles of their self-assumed privileges and reinforced the king's sole authority to confer rank and status.

Under Li Yu's reign, the An Lushan Rebellion was finally crushed after eight years of war. The rebel state of Yan collapsed, and Tang authority was restored over most of the empire, though the dynasty was permanently weakened.

The Tibetan Empire launched a surprise invasion, capturing the Tang capital Chang'an. Li Yu fled to Shanzhou. The Tibetans installed a puppet emperor before being driven out by Tang forces and Uyghur allies. This exposed Tang military weakness.

Li Yu granted amnesty to many rebel generals and allowed them to retain control of their provinces as military governors (jiedushi). This created semi-autonomous fanzhen that weakened central authority and led to future rebellions.

Li Yu negotiated a peace treaty with the Tibetan Empire, establishing a border and ending hostilities for a time. The treaty stabilized the western frontier but did not prevent future conflicts.