Myeongjong era (1558–1567) In 1555, Yun Tusu passed the
Classics Licentiate Examination () in first place. In 1558, he completed the regular civil service examination () and began his governmental career as an editorial examiner () at the . Afterwards, he worked at the
Office of Special Advisors as a proofreader () and later as first copyist (). In 1561, he was appointed as an assistant section chief () for the
Ministry of Military Affairs; in 1562, he became an assistant section chief for the
Ministry of Personnel. Following his return to office, Yun was soon promoted as the section chief () of the Ministry of Personnel. He then transferred to the
State Council, where he served as legal secretary () and then as drafting adviser (). He later went back and forth between the
Office of the Inspector General and
Sungkyunkwan before settling in the . In 1565, he supervised funeral rites at the mourning of
Queen Munjeong during his tenure as assistant responding editor () of the
Office of Special Advisors. After the rites were over, he was selected as the Grand Master of Comprehensive Governance () and was commissioned as the director of the (). On the 7th day, 1st month of 1566, he entered the
Royal Secretariat as the sixth royal secretary () and was later promoted to the right assistant royal secretary (). On the 8th month of 1566, he was appointed as the left assistant royal secretary (). In 1567, while Yun was working as the Right Royal Secretary () at the Royal Secretariat, Myeongjong became bedridden in critical condition. Yun dispatched a letter to Chief State Councilor containing a historical anecdote, citing "
Wen Yanbo of the
Song Dynasty came into the palace and slept"a message urging Yi to reside overnight at the King's residence. Yi Chun'gyŏng followed suit and soon after received Myeongjong's final order deciding on his successor that very night. and the third minister of personnel (). From September 1574, he was put in charge of supervising the civil service examinations, becoming an assistant examiner () the following month. The policies of the early Seonjo era gave rise to a youthful generation of Sarim politicians, who demanded the redressing of past literati purges and the establishment of a system of appointment where junior officials are authorized to nominate meritorious scholars (
seonbi) to office (). They conflicted with elderly officeholders (), who opposed radical reform and insisted that appointment powers are reserved to top-level ministers. Yun Tusu, along with political cohorts , Yi Tak, and , aligned with the Sarimalthough he had been in public service since the era of Myeongjong and was considered a senior politician by then. For instance, in 1570, Yun requested the forfeiture of the titles of merit () that were awarded to those who orchestrated the . By the 1570s, however, Sarim officeholders dominated the political sphere as elderly conservatives died or retired from office. In 1575, the Sarim faction split into two factionsthe
Easterners and the
Westerners. While the division was caused by a dispute between
Sim Ŭigyŏm and
Kim Hyowŏn over the appointment of
Kim Hyowŏn as the section chief for the Ministry of Personnel, it encompassed a larger, structural dissenssion between older and younger Sarim politicians. Yun Tusu joined the Westerners, who were supporters of
Sim Ŭigyŏm and consisted of senior members of the former Sarim. Yun quickly rose as a leading figure among the Westerners as a member of the "Three Yuns"Yun Tusu, Yun Kŭnsu, and Yun's nephew, Yun Hyŏnall of whom held prominent offices in government. In 1576, Yun Hyŏn was appointed as assistant section chief in the Ministry of Personnel. Yun Hyŏn's appointment sparked conflict between incumbent section chief Kim Sŏngil, an Easterner, and Yun Hyŏn's two uncles, who actively suppressed the Easterners. In 1578, a dispute erupted between the two factions when Kim Sŏngil accused the three Yuns of accepting bribes from Magistrate of
Jindo County Yi Su (), which led to the impeachment of the three Yuns by the
Office of the Inspector-General and the Office of Censors. While all three men were eventually reinstated to a government office, the incident marked the first major contention between the two factions. Following the impeachment incident, Yun Tusu grew skeptical of returning to a central government post and took the position of the magistrate of
Naju (). He was later promoted as the magistrate of the
Yeonan Protectorate (), and was granted silk clothes from Seonjo in 1581 for his contributions during a famine. Yun Tusu insisted on sending an address to
Liaodong to announce the war, punishing those who did not come with king as court officials, and remaining in Kaesong and defending. However, when King Seonjo heard that
Kyongsong had fallen, he wanted to leave Kaesong. Yun Tusu requested that the royal carriage leaves early in the morning, but it was not accepted. Accordingly, Yun Tusu sent the governor of Hwanghae to soothe people so that the procession could leave Kaesong safely. The royal carriage left Kaesong on May 3 and arrived in Pyongyang on May 7. On May 9, he became
Left State Councilor. On May 19, discussions took place on asking Ming for relief forces. Yun Tusu objected to this for three reasons. First, Joseon's soldiers are guarding
Imjin River and have enough troops. Second, it is not clear that the Ming government will send troops. Third, the military in Liaodong and
Guangning have a ferocious nature and various villages in
Pyongan Province will be devastated. However, as the situation became increasingly urgent, Yun Tusu also agreed to the request for relief forces. He also insisted on protecting Pyongyang in discussions on whether to protect Pyongyang or move to another place. King Seonjo refused to accept this and asked to discuss the next destination, and Yun Tusu recommended going to
Uiju rather than
Hamhung. The procession left for Uiju, and Yun Tusu remained with to protect Pyongyang. == Family ==