1589 rebellion of Jeong Yeo-rip

The rebellion of Jeong Yeo-rip in 1589, known in Korean as the Gichuk oksa (기축옥사, 己丑獄事), was one of the bloodiest political purges in Korea's Joseon Dynasty. Its scale was greater than all four of the notorious literati purges combined. At that time Joseon politics was dominated by conflict between Eastern and Western factions. Neo-Confucian scholar and Easterner Jeong Yeo-rip was accused of high treason, after which as many as 1,000 Easterners were killed or exiled. (Oksa means a major case involving high treason in Korean, and there were several events named oksa during the Joseon period.)

There is still much dispute about the Treason Case of 1589 because there is a wealth of conflicting historical accounts written by both factions. In the Annals of Joseon Dynasty, the official royal record of the Joseon Dynasty, the Seonjo Annals were written by the Easterners (who held power in Gwanghaegun's reign during which it was written) while the Revised Seonjo Annals were written by the Westerners who later seized power with a coup d'état that placed Injo on throne. In "Yeonryeoshil Records", unofficial history compiled by Yi Geung-don much later, Yi included accounts of the both sides and marked them in different colors to identify them as such.

During King Seonjo's reign, the Sarim scholars following the Kim Jong-jik's school of Neo-Confucianism seized power after long period of perseuction and purges. However, generational difference soon emerged within the Sarim faction - older generation who entered politics during predecessor Myeongjong's reign and younger generation who became officials during Seonjo's time. Their difference was reflected in their attitude toward Shim Eui-gyeom, Myeongjong's brother-in-law. The Sarim tended to regard the king's maternal relatives as corrupting influence on the court and best to be excluded from politics. But older generation, which came to be called the Westerners because Shim's house was on the west of the palace, supported Shim for being Yi Hwang's disciple and protecting them from yet another purge of Sarim that had been planned by his uncle. However, younger generation, called Esterners because its leader Kim Hyo-won's house was on the east of the palace, regarded Shim and older Sarim officials partly responsible for excesses of Myeongjong's reign, which was notorious for corruption and abuse of Yoon Won-hyeong, Myeong's maternal uncle. Philosophically, Easterners tended to be followers of Yi Hwang and Jo Shik while the Westerners followed Yi I and Seong Hun.

...
Wikipedia