Yun Gwan

Yun Gwan led a Goryeo army of 170,000 men against the Jurchen tribes in the northeast, constructing nine fortresses to secure the region. The campaign temporarily expanded Goryeo territory but faced fierce Jurchen resistance.

Yun Gwan built nine fortresses in the conquered Jurchen territories to consolidate Goryeo control. The fortresses became a symbol of Goryeo's northern expansion but were later abandoned due to diplomatic pressure.

Under Jurchen diplomatic pressure and internal court opposition, Yun Gwan was recalled and the nine fortresses were returned to the Jurchen. This reversal undermined his achievements and led to his political downfall.

Yun Gwan was exiled by political rivals after the fortress abandonment, dying in obscurity. His legacy was later rehabilitated as a symbol of Goryeo's military strength and northern ambitions.