Gogukwon’s son and successor, Sosurim, born as Go Gu-Bu and made crown prince in 355, had assisted his father in leading the country and strengthening royal authority.

Turning to domestic stability and the unification of various conquered tribes, he establishes state religious institutions to transcend tribal factionalism.

Having received Buddhism through traveling monks of Former Qin, he builds temples to house them, embracing Buddhism as the national religion in 372.

In the same year, he establishes a national educational institute called the Taehak, a Confucian institution meant to educate the children of the nobility.

Sosurim promulgates a code of laws in 373 that centrally codifies regional customs and serves as the national constitution.

King Sosurim of Baekje has attacked the Korean kingdom of Baekje to the south in 374, 375, and 376, and in 378 is attacked by the Khitan people from the north.

King Sosurim has spent most of his reign and life trying to keep Goguryeo under control and strengthening royal authority.

Although he is not able to avenge the death of his father and previous Goguryeo ruler, King Gogugwon, he has played a major role in setting up the foundations that make possible the great conquests of his nephew and later ruler of Goguryeo, King Gwanggaeto the Great.

He dies in 384 and is buried in Sosurim, which is a forest in Goguryeo.