Goguryeo: An ancient Korean kingdom (c. 37 B.C. - 668 A.D.), which controlled an area from the southern Russian Maritimes to the central Korean Peninsula, including large sections of Manchuria.
Goguryeo was one of Korea's "Three Kingdoms," along with Silla and Baekje. The three performed an uneasy diplomatic waltz, sometimes fighting one another, and at other times banding together to fight outside threats.
The Goguryeo Kingdom was defeated in 668 by the Silla, in confederation with China's Tang Dynasty. The Silla unified all of the Korean Peninsula as "Unified Silla," which lasted until 935 CE.
The English-language name "Korea" is said to derive from the Goryeo Dynasty (918-1392), which in turn took its name from the earlier Goguryeo Kingdom.
"The Gogoryeo King Sosurim established Buddhism as the national religion in 372 CE."