Creation of the Byeolmuban
Outmatched by Jurchen cavalry, Goryeo formed the Byeolmuban, a special army of cavalry, infantry and warrior monks, on Yun Gwan’s advice.
In the early 12th century the Jurchens, united under the Wanyan clan, pushed down to Jeongju, and Goryeo lost two battles in 1104. Yun Gwan reported that "the enemy rode horses while we fought on foot" and proposed a special force.
The Byeolmuban comprised the Singigun cavalry, the Sinbogun infantry and the Hangmagun of monks. Anyone with a horse — from officials without posts to clerks, merchants and slaves — joined the cavalry, and the rest the infantry.