As is true of all countries the geography of Korea shaped its history, including the manner in which the inhabitants of the peninsula emerged as a people sharing the common feeling of being Koreans. The Korean peninsula sticks out southward from the northeastern corner of the Asian continent and is surrounded on three sides by large bodies of water. Although a large portion of Korea was surrounded by water, many events occurred on Korea in ancient times was affected by the civilizations on the Asian continent.
2. Geography of the Korea Peninsula
Since the Yalu and Tumen rivers have long been recognized as the border between Korea and China it is easy to think that these rivers have always established Korea’s northern boundaries. But this was not the case in the ancient period. Neither of these rivers was considered to be the official borderlines by the ancient tribes that existed around the plains of Manchuria and the Korean peninsula. Since the rivers become frozen in the winter large armies could easily cross without difficulty. Even when they were not frozen, armies equipped with iron tools could easily solve the technical problem by building ships to cross them.
3. The Three Kingdoms
Until A.D. 313, Korea was considered to be under Chinese rule. However, Koguryo, the first of three indigenous kingdoms that were soon to emerge, finally officially kicked out the Chinese. For some 400 years Lolang, the core of the colony, became a great center of Chinese art, philosophy, industry, and commerce. Many Chinese immigrated into this area. Therefore it strongly influenced Korean culture even after overthrowing the Chinese. The tribal states south of the Han River played an important part to the Chinese and helped shape much of their civilization and government after them.
The part of Korea south of the Han River is relatively distant from the Asian continent. Therefore, the people living there were initially able to develop on their own without many problems such as wars and invasions on their home territory. The early settlers of this region little by little organized themselves into about approximately seventy clan states. Those seventy clan states were in turn grouped into three tribal confederations known as Chin-Han, Ma-Han, and Pyon-Han. Chin-Han was began and developed in the middle part of the peninsula. Ma-Han on the other hand was situated in the southwest. And Pyon-Han was settled in the southeast. All three tribal confederations based their economics predominantly agricultural objects such as rice. They were extremely advanced and efficient with agriculture. Their level of development was such that they built reservoirs and irrigation facilities. These tribal states, the Chin-Han, Ma-Han, and the Pyon-Han, began to be affected by what was happening in the region north of the Han River around the first century B.C.
About the middle of the third century A.D. the Chinese started to get aggressive again. The Chinese threat was powerful to a point where the individual tribal confederations had very little chance of resisting the invasion. Although the threat from China brought a lot of distress amongst the Korea, this was the first step in unifying the three kingdoms of Korea. The loose confederations of tribes in the southern part of the Korean peninsula became politically unified. They adopted the Chinese political system as a model and merged into two kingdoms. By doing this, their chance of survival against Chinese expansionism was increased. The two kingdoms eventually came to play an important role in Korean history.
The southern tip of the Korean peninsula is mostly composed of mountain ranges. The geography of southern Korea caused two kingdoms to politically unify and emerge rather than stand on its own. In the central part of Korea there is a main mountain range called the T’aebaek Range. This mountain range runs north to south along the edge of the Sea of Japan, which lies off the East Coast of the peninsula. Approximately about three-fourths of the way down the peninsula, however, (at roughly the thirty-seventh parallel) the mountain range curves towards the southwest, thus dividing the peninsula almost right split in the middle. This extension, (also called the Sobaek Range) proves to be politically significant due to a reason. The tribes west of the Sobaek Range were not shielded by any sort of natural barriers that protected them from the Chinese-occupied portion of the peninsula. On the other hand, those to the southeast of the mountain range were protected. Moreover, it prevented the tribes in the two regions from establishing close contacts. This meant that the natural barriers played a role in preventing tension between the tribal states in Korea.
The tribal states in the southwest were the first to unite. They called their centralized kingdom Paekche. This occurred sometime in the middle of the third century A.D. after the Chinese army of the Wei Dynasty (A.D. 220-264), which controlled Lolang, threatened the tribes in A.D. 245. In the southeast, the Silla kingdom evolved. Silla historians traced the kingdom’s origin to 57 B.C., but contemporary historians regard King Naemul (A.D. 356-402) as having been the earliest ruler. Some of the tribes located in the south central tip of the peninsula facing the Korea Strait did not join either of these kingdoms. Instead, they maintained very close political ties with the tribal states in Japan. Due to the fact that these Kaya League states were sandwiched between the more powerful Silla and Paekche, they were eventually absorbed by their neighbors. There was a Japanese attack against Silla on the behalf of the Kaya League states in A.D. 399. However, Silla repelled them with the help from the northern kingdom of Koguryo.
The kingdom of Koguryo emerged among the indigenous people around the banks of the Yalu River. Han Chinese took over the area in 108 B.C.. The Chinese rulers strictly did not tolerate any uprisings against their rule. Starting from a point along the Hun River (a tributary of the Yalu), the people who rebelled against the Chinese authority little by little expanded to the north, south, and southeast. By A.D. 53, Koguryo had unified into a single independent centralized kingdom. The Han Dynasty collapsed soon after the formal establishment of the Koguryo. In addition, China became politically divided following the fall of the Han Dynasty. These two factors were a huge factor for Koguryo to effectively strengthen and extend its power. The kingdom faced continuously repeated attacks by Chinese and other opposing forces. However, such attacks and invasions did not stop the expansion of the kingdom of Koguryo.
By A.D. 391, the kingdom had achieved undefeatable control of all of Manchuria east of the Liao River as well as the northern and central regions of the Korean peninsula. Its best known ruler, King Kwang-gae-t’o — whose name literally means “Wide Open Land” — lived to be only thirty-nine years of age but reigned twenty-one years, from 391-412. During that period he bravely conquered sixty-five walled cities and 1,400 villages. In addition, he helped the Silla kingdom when it was attacked by the Japanese. His accomplishments are recorded on a monument erected in A.D. 414 in southern Manchuria. Koguryo moved its capital to P’yongyang in A.D. 427 and ruled the territory north of the Han River. But Koguryo’s expansion caused it to come into conflict with the Sui Dynasty of China (581-618) in the west and Silla, which was beginning to expand northward, in the south.
For a long period of time, Koguryo was strong enough to fight against the forces of the Sui Dynasty. However, one can only resists for so long. The repeatedly combined attacks from the Silla and the Tang Dynasty of China (618-907) gradually came to be too unbearable for the Koguryo. The Koguryo Kingdom’s ally in the southwest was the Paekche. However, the Paekche fell before Tang and Silla in A.D. 660. Therefore, Koguryo was not able to receive aide when they needed military help. The victorious allies continued their assault on Koguryo for the next eight years. At this time, the kingdom was suffering from a series of famines and internal strife. The Koguryo kingdom was weakened little by little, and eventually the weary kingdom was vanquished.
4. Unified Korea Under Silla
Silla thus unified Korea in A.D. 668. However, because the Silla kingdom highly relied upon China’s Tang Dynasty, Silla had to pay its price. Eventually Silla had no choice but to resist by force the imposition of Chinese rule over the entire peninsula of Korea. Although they were able to effectively resist Chinese rule, the Silla were not powerful enough. Silla’s strength was not able to extend beyond the Taedong River. Almost all of the territory the Koguryo kingdom used to rule was given up to the Chinese and the other tribal states. The former territory of Koguryo remained for later dynasties to gradually push the border northward to the Yalu and Tumen rivers. Thus, the events of the seventh century largely delimited the territory of what was to become Korea.
The first 215 years of the Silla Dynasty were highly impacted and many factors led to the strengthening and unification of Korea. The establishment of brand new political, legal, and educational institutions were practiced and brought about. Domestic and foreign trade (with Tang China and Japan) prospered highly. In addition, scholarship in Confucian learning, mathematics, astronomy and medicine also flourished greatly. And finally, Buddhism was also introduced to the Korean peninsula in A.D. 372, and greatly influenced the people.
The Silla kingdom, however, began to decline towards the later years of the eighth century. This was due to the rebellions within the kingdom, which shook its foundations. Little by little, the rebellions became out of hand. By the latter half of the ninth century two rivals had emerged. The extremely chaotic situation eventually led to the fall of the Silla kingdom, and resulting in the emergence of Koryo Dynasty in 932 under a former general, Wang Kon.