The faction was consisted of the opponents of Song Siyeol after the split of the Westerners.
After the Injo coup of 1623 that led to the replacement of king Gwanghaegun of Joseon with Injo of Joseon, political faction Westerners, who gained political power as a result of the event, was split into two factions, which were Hunseo (who actively participated in the coup, 勳西) faction, also called Gongseo (功西), that was led by Kim Ryu (金瑬) and the Cheongseo (Westerners who did not actively participate in the coup, 淸西) faction led by Kim Sang Heon (金尙憲).
Cheongseo faction was also similarly split in two, the san faction (Mountain party), which were led by the sarims originated from Goesan and Hoedeok counties which values the purity of scholars that are not influenced by power, and the Han faction (people in the capital Hanseong, modern day Seoul) who tried to fit the needs of the people in power.
Songsiyeol who was against this appeal became the leader of the political faction Noron, and the faction who supported the appeal led by Yun Jeung, who was a disciple of Song si yeol became Soron.
[1] Soron faction gained in power in 1694 as a result of Gapsul Hwanguk.