Peroz I vs Sansang of Goguryeo

Peroz I's reign was marked by a severe famine and economic hardship, exacerbated by his military campaigns. The crisis weakened the Sasanian economy and led to social unrest, undermining the stability of the empire.

Peroz I was captured by the Hephthalites during an earlier campaign and held for ransom. He was released after paying a large tribute, but the humiliation fueled his desire for revenge, leading to his final disastrous campaign.

Peroz I launched a military campaign against the Hephthalite Empire (White Huns) in Central Asia. The campaign ended in a decisive defeat for the Sasanian army, with Peroz I killed in battle and his army annihilated, leading to a period of instability in the Sasanian Empire.

Upon ascending the throne, Sansang married his deceased brother Gogukcheon's widow, Queen U. This marriage was controversial but helped consolidate his claim to the throne and maintain continuity with the previous reign.

The Han dynasty of China launched a major invasion of Goguryeo, capturing several border fortresses. Sansang led the defense, ultimately repelling the invasion but suffering significant territorial losses in the Liao River region.

After the Han invasion, Sansang ordered the fortification of Gungnae Fortress and other key defensive positions. He also reorganized the military command structure to better respond to future Chinese threats.