The Gisa Hwanguk (Korean: 기사환국) occurred when[when?]
the Westerners fell out of power after opposing the naming of a crown prince by Sukjong of Joseon.
King Sukjong decided to abandon the previous system of party alliance and replace it frequently in order to stabilize his authority.
In the beginning of King Sukjong's reign, the Southerners took the lead with the victory of the second Yesong.
In response, the Westerners felt a sense of crisis as a political opponent of the Southerners, and the King Sukjong also had a sense of caution about the continuing rule of the Southerners.