[8] The incident resulted in a large political debate on whether Kim Hyowon's actions were just, titled the Eulhae Dangron ('factional strifes of 1575').

[11] In the 1570s, the conflict between the Easterners and Westerners intensified, despite efforts by people such as Yi I or Seong Hon to reconcile the hostile groups together.

[12] In 1575, Yi I was an advisor to Seonjo, and advised the king to send both Kim Hyowon and Sim Euigyeom as officials in faraway counties.

Seonjo then moved Kim Hyowon as a governor of Samcheok, a town slightly larger than Buryeong, 150 kilometers to the east of Seoul.

[13] However, the Easterners, who were by far the majority in court, were not pleased that Yi I was apparently neutral in the conflict, when they believed that Sim Euigyeom had clearly wronged.

However, Sim had interfered in politics despite his status as a relative of the queen, while Kim had been close to Yun Won-hyeong despite his being a Seonbi.

However, Jeong added the single sentence "gathers other officials to create a faction" in the list of Sim's misdeeds in the advice.

Jeong Cheol, Seong Hon, and Sim were fired,[16] creating a solidly Easterner government for five years until 1589.

[17] Yi I and Seong Hon were ferociously attacked by Easterners, often on the charges that they had attempted to create a faction.

Though controversial,[19] mainstream historians generally believe that Yi I advised the king to prepare 100,000 soldiers against possible foreign invasions.

[22] Jeong was also an ideologue, who believed that "the world is public property, with many owners",[23] and that "Yao and Shun became great because they gave power to the talented and not to their sons.

However, there is an opposing theory, suggested by the Easterners ever since the purge, that the Westerners killed Jeong and disguised his murder as suicide.

[27] In 1590, the Easterners Yi Sanhae and Yu Sŏngnyong and the Westerner Jeong Cheol were the three State Counciliors - the Samjeongseung (삼정승).

Prince Imhae, the oldest one, was known for stealing the properties of peasants, drinking alcohol, and being friends with gangsters.

[29] However, Yi Sanhae knew that Seonjo was much closer to Royal Noble Consort Inbin Kim and her eldest son, Prince Sinseong, over either Imhae or Gwanghae.

Yu Sŏngnyong was too cautious to bring the subject up, and Jeong Cheol was the first to advise Seonjo to make Gwanghae Crown Prince.

When Jeong Cheol brought the matter up, Seonjo was infuriated, believing that the story told by Consort In was true.

Seonjo exiled Jeong Cheol and fired Westerners such as the Yun Du-su brothers, recreating a solidly Easterner government.

[31] Meanwhile, in 1590 (when the Easterners regained power), the warlord Toyotomi Hideyoshi unified Japan, ending the Sengoku period.

[12] According to the Easterner Yu Sŏngnyong in his Jingbirok, the reason for Kim's saying that Japan would not invade was to stop the people from being frightened or rioting.

[e] However, Hwang proved ultimately correct, as Toyotomi invaded Busan with 200,000 soldiers in 1592, and the unprepared government collapsed at the onslaught.

Most of the Easterners who wanted to kill Jeong lived near Mount Bugak (translated to the Northern rock), while most of the Easterners who opposed killing Jeong lived near Mount Nam (translated to the Southern mountain).

[35] The students of Jo Sik had suffered terrible damages by Jeong Yeorip's purge, while the followers of Yi Hwang had not lost anyone.

[12] Moreover, Yu Sŏngnyong, the most influential of Yi Hwang's students, retained a close relationship with Jeong Cheol, who led the purge.

[35] Another cause for division was that Jeong In-hong, the most favored student of Jo Sik, had a contempt for Yi Hwang and his pupils, who formed a large part of the Easterners.

[36] By 1598, the split of the Easterners had become apparent, with Southerners such as Yu Sŏngnyong being attacked by Northerners such as Yi Yicheom.

[38] The ideologies of the Easterners were very diverse, including pupils of Jo Sik, Yi Hwang, and Seo Gyeongdeok.

[36] The people who formed the Easterners were largely of the Yeongnam School of philosophy, which included Jo Sik and Yi Hwang.