One of the biggest and strongest ancient Korean empires. It can also be written as Goguryo. Kukuryo was at the northern part of Korea and was a huge threat to other countries- such as some Chinese dynasties or other Korean empires. Kokuryo owned a chunk of land that was about the size of nowadays' China. However, even though it is certainly and obviously one of the biggest Korean empires, China is arguing that Kokuryo was their history, coming out with some stupid reasons that don't even make any sense at all.
Kokuryo was one of the biggest ancient Korean empires and was one of the biggest empires in the world at the same time.