In the mid-4th century, Goguryeo faced significant challenges. Externally, frequent wars with neighboring states like Baekje and Former Yan drained national power. Internally, the strong autonomy of various tribal factions made the strengthening of royal authority and national integration an urgent necessity. King Sosurim inherited a kingdom that had suffered a severe crisis, including the death of his predecessor, King Gogukwon, in battle against Baekje. He was tasked with stabilizing this turmoil and establishing a powerful centralized system. Traditional shamanism and local cults were fragmented and insufficient to unite the divided populace or firmly establish royal authority. To address this, King Sosurim officially accepted Buddhism in 372, introduced by the monk Sundō from Former Qin. Buddhism, with its universal truths, served as a powerful governing ideology. It sanctified royal power by portraying the monarch as a 'Chakravartin' (wheel-turning king), a protector of the dharma, and encouraged the populace to accept the current social order through concepts like karma and reincarnation. Simultaneously, the king established temples such as Ibullansa and Seomunsa in the capital, laying the groundwork for Buddhism's nationwide spread. In the same year, King Sosurim founded Taehak, a national Confucian academy. Its purpose was to educate the children of the aristocracy in Confucian classics, history, and law, a crucial step for training central bureaucrats and efficiently operating the state's administrative system, including the *yullyeong* (legal and administrative codes). King Sosurim's acceptance of Buddhism and establishment of Taehak marked a revolutionary turning point in Goguryeo's history. Buddhism played a decisive role in unifying fragmented tribal forces and strengthening royal authority, while Taehak nurtured talented individuals, establishing a centralized governance system and laying the foundation for the promulgation of *yullyeong*. Through ideological unification and administrative system reform, Goguryeo was able to develop into a powerful ancient state. This provided a solid foundation for the territorial expansion and golden age under King Gwanggaeto and King Jangsu. Furthermore, Goguryeo's progressive adoption of advanced culture influenced Baekje and Silla, profoundly impacting the overall state development and cultural formation throughout the Three Kingdoms period.