Chapter 5: Three Kingdoms Era

About the middle of the third century AD, the Chinese threat began to serve as a unifying political force among the loose confederations of tribes in the southern part of the Korean peninsula. Adopting the Chinese political system as a model, the tribes eventually merged into two kingdoms, thereby increasing their chances of survival against Chinese expansionism. Geographic features of the southern parts of the peninsula, in particular the configuration of mountain ranges, caused two kingdoms to emerge rather than one. The two kingdoms eventually came to play an important role in Korean history.

In the central part of Korea, the main mountain range, the Taebaek Range, runs north to south along the edge of the Sea of Japan, which lies off the east coast of the peninsula. However, approximately three-fourths of the way down the peninsula, at about the thirty-seventh parallel, the mountain range veers southwest, dividing the peninsula almost in the middle. This extension is called the Sobaek Range. Tribes west of it were not shielded by any natural barriers against the Chinese-occupied portion of the peninsula, whereas, those to the southeast were protected. Moreover, the presence of the mountains prevented the tribes in the two regions from establishing close contacts. These two regions began to develop into separate entities.

The Silla Kingdom (57 BC - 936 AD) was the first to develop. It was formed on the southeastern Kyongju plain by a confederation of six clans of the Chin-han. The tribal states in the southwest united, calling their centralized kingdom Paekche (18 BC - 600 AD). Some of the tribal states in the area of the lower Naktong River, along the south central coast of the peninsula, did not join either of these kingdoms. They formed a league of walled city-states, called Kaya, which conducted extensive coastal trade and also maintained close ties with the tribal states in western Japan. Sandwiched between the more powerful Silla and Paekche, Kaya eventually was absorbed by its neighbors during the sixth century. The northern kingdom of Koguryo (37 BC - 668 AD) emerged from among the indigenous people along the banks of the northern Yalu River. It formed after Silla and before Paekche and was the largest of the three. Koguryo, Paekche, Silla formed the three kingdoms of ancient Korea.