Behind the Seo Hui submarine: Goryeo, the dynasty that gave Korea its name

Background

South Korea's Navy set a launch ceremony this week for a new submarine named after Seo Hui, a diplomat of the Goryeo Dynasty.
Goryeo ruled a reunified Korea from 918 to 1392.
The English name 'Korea' comes from the name Goryeo.
Before it, the Three Kingdoms of Goguryeo, Baekje and Silla had divided the peninsula and Manchuria, and Silla unified Korea from 668 until it broke apart in 935.
Goryeo was followed by the Joseon Dynasty.
Today South Korea's capital is Seoul and its language is Korean.