Emperor Xianzong of Tang vs Gangjong of Goryeo

Emperor Xianzong initiated the Yuanhe Restoration, a series of reforms aimed at centralizing power and curbing the autonomy of military governors (jiedushi). He reasserted imperial authority over several rebellious provinces, strengthening the Tang state.

Emperor Xianzong launched a military campaign against the Chengde Circuit, a rebellious province in Hebei. After initial setbacks, the Tang forces secured a victory, forcing the Chengde governor to submit to imperial authority.

Emperor Xianzong's forces conquered the Zhaoyi Circuit, a rebellious province in modern Shanxi. This victory further reduced the power of the military governors and strengthened imperial control.

Emperor Xianzong launched a campaign against the Pinglu Circuit in Shandong. The Tang forces defeated the rebel governor, bringing the province back under imperial control and completing the Yuanhe Restoration's military successes.

Emperor Xianzong died suddenly, possibly poisoned by eunuchs. His death ended the Yuanhe Restoration, and subsequent emperors were unable to maintain the centralization he achieved, leading to the Tang dynasty's further decline.

Gangjong became king after his brother Huijong was deposed by Choe Chung-heon. His reign coincided with the first Mongol invasions of Goryeo, though he had no authority to direct military policy.

Like his predecessors, Gangjong was a puppet king under the Choe military dictatorship. All major decisions, including responses to the Mongol threat, were made by Choe Chung-heon and his private army.

Gangjong died in 1213, just as Mongol forces under Genghis Khan began their first major campaign against Goryeo. His brief reign of two years saw no significant policy changes, and the Choe regime continued to dominate.