This letter of appointment was issued by the Joseon king Seonjo, and names Kayashima Mokubei, a retainer of the Mōri family, as a military officer of Joseon. It is accompanied by two letters by Hong Isang, an observation and patrol officer of Gyeongsang-do, relating to the appointment. These three documents were issued between the eighth and tenth months of 1594.
As per the practice in the Joseon Kingdom, bureaucrats of rank four and above were appointed directly by the king himself. In such cases, the document issued follows the format of a gyoji 敎旨, or a royal decree, of which this letter is an example. According to the letter, Kayashima was appointed the jeolchi janggun 折衝将軍, a senior third-rank (upper) military officer who was to act as the sang hogun 上護軍 (senior guard) of the Yongyangwi 龍驤衛, one of the five guards (units) of the Joseon army. The seal of the king, which reads shimyeong ji bo 施命之宝 (lit., “treasure that issues commands”), is stamped where the date is written, as in all royal decrees of the fifteenth and sixteenth centuries.
The first of the two related documents is a letter written by Hong Isang to Song Changse, a student from Dongnae. It commends the latter’s contributions in delivering enemy information and securing Kayashima’s defection to Joseon. The second letter, also written by Hong, is a reply to a letter from Kayashima. Dated two months after the appointment letter, Hong urges Kayashima to defect to Joseon, as the latter had yet to make his loyalties clear despite having accepted the appointment.
These three documents come from the peace negotiations that took place during the first of Japan’s invasions of Joseon. Just when negotiations between Japan and Ming China were reaching a stalemate (Joseon was completely left out of the discussions), a few of the daimyo who had established “Japanese cities” along the southern coast of Joseon, including the Mōri family, saw numerous deserters and defectors, whose decisions had been influenced by Joseon itself. Reports pertaining to these soldiers can be found in the Veritable Records of the Joseon Dynasty, and provide further details regarding the circumstances of Kayashima’s defection and the creation of these three documents. In particular, we can see how the Joseon Kingdom had invited an invading Japanese warrior into their ranks as a strategic move.
Until the early Shōwa period, these documents belonged to the Awaya family, who were distant relatives of the Kayashima family. They later joined the Kyushu National Museum collection, and are being kept together with four other early-modern documents from the Awaya family, all related to this appointment.