The Relationship between Baekje and Japan during the Reign of King Mu: The Role of Buddhism : Focusing on the Monk Gwanreuk

The relationship with Japan was of paramount importance in Baekje's foreign relations during the reign of King Mu. After his ascension to the throne, Baekje faced significant challenges in its diplomatic interactions with both China and the other Three Kingdoms. In light of these internal and external difficulties, King Mu strategically decided to send the monk Gwanreuk to Japan. This initiative was informed by the context in which Japan was strengthening its centralization through the promotion of Buddhism. As a result, Baekje was able to secure a preeminent position in its relations with Japan, effectively leveraging Buddhism as a central element of this diplomatic engagement, distinguishing itself from the other kingdoms. The Baekje monk Gwanreuk was active at Beopheungsa, the first temple in Japan. As the teacher of Prince Seongdeok, he instructed in Buddhist doctrine and established a close relationship with the ruling class of Japan by teaching them calendar systems, astronomy, geography, and sorcery. Gwanreuk's efforts significantly contributed to the strengthening of royal authority in Japan through Buddhism. Subsequently, in 624, he became the first monk to attain the position of Seungjeong in Japan, where he played a pivotal role in organizing the Buddhist community centered around Baekje Buddhism. The Baekje monk Gwanreuk was active in Japan for over twenty years, from 602 to 624. His activities must be understood in the context of Baekje's relations with Japan. Following Gwanreuk's transfer, Baekje and Japan continued to engage in exchanges centered around Buddhism. However, around the year 624, Japan began to seek assistance from Silla to establish ties with the Tang Dynasty and appointed the Goguryeo monk Hyegwan as a new Seungjeong in 625. This shift indicates that Japan was moving away from a foreign relations framework centered on Baekje and was now exploring independent diplomatic avenues.