Wikipedia
Byeolmuban
Byeolmuban is the name of a special army unit in the time of Korea's Goryeo Dynasty (918–1392). The word byeol literally means star, but also has the meaning of special. Founding of the army was initiated by Yun Gwan during the reign of king Sukjong of Goryeo.
The army was put together to fight the Jurchen who were putting pressure on Goryeo's northern borders. The Goryeo infantry had a hard time resisting the strong Jurchen cavalry.