Saedae was a government office of the Taebong

Taebong

Taebong or Later Goguryeo was a state established by Gung Ye on the Korean peninsula in 901, during the Later Three Kingdoms period.-History:...

 state (also known as Later Goguryo or Majin), a short-lived kingdom (901–918) founded by Gung Ye

Gung Ye

Gung Ye was the king of the short-lived Hugoguryeo on the Korean peninsula. Although he was a member of the Silla royal family, he became a victim of the power struggle among the royal family members during the late 9th century...

 during the Later Three Kingdoms period

Later Three Kingdoms

The Later Three Kingdoms of Korea consisted of Silla, Hubaekje , and Hugoguryeo . The latter two were viewed as heirs to the earlier Three Kingdoms of Korea, which had been united by Silla, even though Hugoguryeo has little to do with Goguryeo...

 (892–936) of Korea.

According to historical records in Samguk Sagi

Samguk Sagi

Samguk Sagi is a historical record of the Three Kingdoms of Korea: Goguryeo, Baekje and Silla. The Samguk Sagi is written in Classical Chinese and its compilation was ordered by Goryeo's King Injong Samguk Sagi (History of the Three Kingdoms) is a historical record of the Three Kingdoms of...

("History of the Three Kingdoms"), as Gung Ye changed the name of the state to Majin (摩震) and named the era "Mutae" (武泰) in 904, he revised the administrative system in reference to those of Silla

Silla

Silla was one of the Three Kingdoms of Korea, and one of the longest sustained dynasties in...

. In the process, he established Gwangpyeongseong (廣評省), the highest administrative office which consisted of 18 departments called Gwanbu including Sadae and Byeongbu (兵部). The Saedae office took charge of education on yeogeo or foreign language. According to the records, learning foreign languages was regarded as important in ancient Korean society.