Usan-guk, or the State of Usan, occupies Ulleung-do and the adjacent islands during the Korean Three Kingdoms period.

According to the Samguk Sagi, General Kim Isabu of the Silla Dynasty conquers the island nation in 512.

According to Sejong Sillok, Goryeosa, and Mangi Yoram, Usan-guk consisted of Ulleung-do and Usan-do.

Koreans believe Usan-do is Liancourt Rocks (Dokdo in Korea, Takeshima in Japan).

Japanese researchers have claimed the various references to Usan-do refer at different times to Jukdo, its neighboring island Ulleungdo, or a nonexistent island between Ulleungdo and Korea.

Usan-guk, or the State of Usan, occupies Ulleung-do and the adjacent islands during the Korean Three Kingdoms period.

According to the Samguk Sagi, it was conquered by the Silla general Kim Isabu in 512.

He is said to have used wooden lions or tigers to intimidate the residents into surrendering.

Usan-guk rarely enters into historical records, but appears to have continued a largely autonomous existence until its annexation to Goryeo in 930.

…Ulleungdo, an island in the Sea of Japan about one hundred and twenty kilometers (seventy-five miles) east of the Korean Peninsula and a recurrent security headache for the Goryeo, is abandoned because of the massive attacks of the Jurchen pirates.

The invasion in 1019 is one of those incidents.