Spread to Japan and Korea
Go was introduced to both Japan and Korea?where it is called baduk (hangul: ??)?somewhere between the 5th and 7th centuries AD, and was popular among the higher classes. In Korea, the game was developed into the variant called Sunjang baduk by the 16th century. Sunjang baduk became the main variant played in Korea until the end of the 19th century.

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Korean players, in traditional dress, play in a
photograph dated between 1910 and 1920.

Korean players, in traditional dress, play in a photograph dated between 1910 and 1920.
In Japan?where it is called go (??) or igo (???)?the game became popular at the Japanese imperial court in the 8th century, and among the general public by the 13th century. In 1603, Tokugawa Ieyasu re-established Japan's unified national government. In the same year, he assigned the then-best player in Japan, a Buddhist monk named Nikkai (n? Kan? Yosaburo, 1559), to the post of Godokoro (Minister of Go). Nikkai took the name Honinbo Sansa and founded the Honinbo Go school. Several competing schools were founded soon after. These officially recognized and subsidized Go schools greatly developed the level of play and introduced the dan/kyu style system of ranking players. Players from the four schools (Honinbo, Yasui, Inoue and Hayashi) competed in the annual castle games, played in the presence of the shogun.