King Sosurim of Goguryeo became king in 371 when his father King Gogugwon was killed by the Baekje King Geunchogo's assault on Pyongyang Castle.

Sosurim is considered to have strengthened the centralization of authority in Goguryeo, by establishing state religious institutions to transcend tribal factionalism. The development of centralized government system was largely attributed to reconciliation policy of Sosurim with its southern opponent, Baekje.

The year 372 held its critical importance in Korean history not only for Buddhism but also for Confucianism and Daoism. Sosurim also established the Confucian institutions of Taehak (태학, 太學) to educate the children of the nobility. In 373, he promulgated a code of laws called (율령, 律令) which stimulated the institutionalized law systems including penal codes and codified regional customs.

In 374, 375, and 376, he attacked the Korean kingdom of Baekje to the south, and in 378 was attacked by the Khitan from the north. Most of King Sosurim's reign and life was spent trying to keep Goguryeo under control and also strengthening royal authority. Although he was not able to avenge the death of his father and previous Goguryeo ruler, King Gogugwon, he did play a major role in setting up the foundations that made the great conquests of his nephew and later ruler of Goguryeo, King Gwanggaeto the Great achieve reckless subjugations.