Korea is a historic country in East Asia, since 1945 divided into two distinct sovereign states: North Korea (officially the "Democratic People's Republic of Korea") and South Korea (officially the "Republic of Korea"). Located on the Korean Peninsula, Korea is bordered by China to the northwest and Russia to the northeast. It is separated from Japan to the east by the Korea Strait and the Sea of Japan (East Sea). 

Korea emerged as a singular political entity after centuries of conflict among the Three Kingdoms of Korea, which were unified as Later Silla to the south and Balhae to the north. Later Silla divided into three separate states during the Later Three Kingdoms period. Goryeo, which had succeeded Goguryeo, defeated the two other states and united the Korean Peninsula. Around the same time, Balhae collapsed and its last crown prince fled south to Goryeo. Goryeo (also spelled as "Koryŏ"), whose name developed into the modern exonym "Korea", was a highly cultured state that created the world's first metal movable type in 1234. However, multiple invasions by the Mongol Yuan Dynasty during the 13th century greatly weakened the nation, which eventually agreed to become a vassal state after decades of fighting. Following the Yuan Dynasty's collapse, severe political strife followed, and Goryeo eventually fell to a coup led by General Yi Seong-gye, who established Joseon in 1392.
When did Korea become one country?
During these conflicts, what was the southern kingdom called?
And the northern kingdom?
Which kindom does Korea take its name from?
What did it invent?
Whom did it become subordinate to?
When?
What succeeded Goryeo?
Who caused that?
What gave him the opportunity to do that?
Caused by?
When did Korea split again?
Which is referred to as the DPRK?
How many countries does Korea share a land border with?
What are the names of the two countries?
What country does Korea share a sea border with?
after centuries of conflict
after centuries of conflict
Silla
Silla
Balhae
Balhae
Goryeo
Goryeo
metal movable type
metal movable type
Mongol Yuan Dynasty
Mongol Yuan Dynasty
13th century
13th century
Joseon
Joseon
Yi Seong-gye
Yi Seong-gye
severe political strife
severe political strife
Yuan Dynasty's collapse
Yuan Dynasty's collapse
since 1945
since 1945
North Korea
North Korea
Two
China to the northwest and Russia 
China and Russia
China
Japan
Japan