Kim Busik presents the Samguk sagi, the oldest surviving history of Korea

Goryeo had just passed through a decade of upheaval: the revolt of the king's maternal grandfather Yi Ja-gyeom in 1126, the acceptance of Jin overlordship in the same year, and the rebellion of the monk Myocheong, who wanted to move the capital to Pyongyang and was crushed in 1135–1136 by an army under Kim Busik. Kim, a scholar-official of the Gyeongju Kim clan descended from the Silla royal house, then led the government until he retired in 1142. When work on a history of the Three Kingdoms began is not known — after Myocheong's defeat or in 1142 — but in the memorial presenting the work Kim quotes the king's lament that the scholars and officials of the day could discuss the Chinese classics and histories in detail, yet knew nothing of their own country's past.

The work was presented to King Injong on the 22nd day of the twelfth month of his 23rd year; the last lunar month of that year, which followed an intercalary month, began on 14 January 1146, so the day fell on 4 February 1146, although the history is conventionally dated to 1145. Kim headed a team of eleven, himself included, and is thought to have written the prefaces and the historical comments himself. The fifty books comprise 28 books of basic annals — twelve for Silla, ten for Goguryeo and six for Baekje — three of chronological tables, nine of monographs on rites, music, dress, geography and offices, and ten of biographies, three of them devoted to the Silla general Kim Yu-sin. The compilers drew on the lost Old History of the Three Kingdoms and other Korean records and borrowed heavily from the Chinese histories.

The Samguk sagi treats the three kingdoms as equals, giving each its own basic annals and calling each ‘our’ state in its own annals, but Silla receives the most space, and the monographs describe mainly Silla. Later critics reproached it for a Confucian, China-centred outlook; it did not count Balhae as a Korean state, and its early dates for the founding of the kingdoms are disputed. In 1174 a copy was sent to the Song court. Together with the Samguk yusa, compiled by the monk Iryeon in the 13th century, it remains the basic source for the history of Korea before the 10th century.