As a descendant of Silla's founder Hyeokgeose, his surname was Park. His title was Isageum, also recorded as Ijilgeum or Chijilgeum. This title is a change from Geoseogan and Chachaung. The actual Silla word is thought to be Itgeum . Imgeum is the modern Korean word for "King".
Background
Yuri was the son of Silla's second ruler, Namhae, and his queen Lady Unje. It is unclear how many siblings Namhae had, but he did have a sister. This sister, Princess Ani, was married to a non-Sillan man named Seok Talhae, who originated from an island nation called Tapana. Talhae became a very highly ranked official and Namhae seemed to prefer him as successor instead of his son. This is revealed on Namhae's deathbed, but Talhae insisted that the prince's rise to the throne would be righteous and allowed Yuri to become the next ruler of Silla.
Reign
According to the Samguk Sagi, the principal source for events of this period, Yuri centralized rule over the aristocracy by turning the six tribes into six official administrative divisions of Silla. He is said to have granted surnames to each of the clans: Yi, Choe, Son, Jeong, Bae, and Seol. He is also said to have created 17 bureaucratic rank levels. However, modern scholars doubt that these occurred so early in Silla's development. Silla was attacked by Lelang commandery and other tribes, but made peace with Maekguk. The Samguk Sagi records that Silla conquered Iseoguk, but this appears to be a mistaken recording of an Yurye-era event. During Yuri's reign, the Silla people celebrated a holiday during the 15th day of the 8th month, where two teams of women would compete in a contest. The losers of the contest would have to prepare songpyeon, rice cakes, meats, fruits, and other food, shared by everyone in a feast. This is said to have been the origin of the modern Korean holiday Chuseok. Also during Yuri Isageum's reign was the rise of the Gaya confederacy as a military power in the region. Silla was under constant rivalry with Baekje already, but Gaya in the middle was even more of a direct threat.
Succession
Yuri Isageum had two sons, but his dying words were to make his brother-in-law, Seok Talhae, his successor to the throne. Yuri Isageum died in 57 AD after 34 years of reign.
