Pyŏlmuban
Pyŏlmuban is the name of a special army unit in the time of Korea's Goryeo Dynasty. The word pyŏl means of special. Founding of the army was initiated by Yun Kwan 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.
Organization
The Pyŏlmuban army had six divisions: Yun Kwan's regular army and Armor Guards called chŏnggyugun Infantry called Sinbogun, Cavalry called Sin'gigun, an army of Buddhist monks called Hangmagun, Supporting troop made of slaves called Yŏnhogun, and volunteered soldiers made of merchants and ordinary citizens called Chubugunhyŏn.Combating troops were divided into Assassin/Spies called Sinbo, Siege Engineers called Tot'ang, Archers called Kyŏnggung, Builders called Chŏngno, Ballistic/Cannon gunners called Palhwa, and special force called T'ŭgibudae. They were to be trained and maintain/make weapons & fight with regular army.
During the second year of king Yejong of Goryeo's reign the Pyŏlmuban, consisting of 17,000 soldiers, attacked Jurchen and killed approximately 5,000 Jurchen troops, detained another 5,000 POWs and 350 Jurchen tribal clans and took over their territory by building nine fortresses at Hamju region.
Fortresses were called Northeastern Nine Fortresses, and they are in Hamju, Yŏngju, Ungju, Pokju, Kilju, Konghŏmjin,, Sungnyŏng, T'ongt'ae, and Chinyang.
However internal trouble at the Goryeo court later forced the Goryeo army to leave Jurchen territory just after few years.