The introduction of bronze precipitated the formation of walled-town states in the northern part of Korean peninsula and Southern Manchuria. Bronze remains are found in most abundance in the Liao River basin and the Taedong River valley, and these remains places the location of GOJOSEON between the two rivers. It may be appropriate here to clear up confusion in the frequent use of JOSEON. The name "GOJOSEON" is used to distinguish the ancient state from JOSEON Dynasty which was founded in l392.
GOJOSEON, the walled-town state, was founded at ASADAL, which proved to be WANGGEOMSEONG presumed to be located at the Taedong River basin. The ruler of the walled-town state was called "DANGUNWANGGEOM." "Dangun" is believed to be a derivative of a Mongolian word, "Tengri", which means "shaman," or "heaven." "Wanggum" is presumed to refer to a political leader, that is, "King." Putting the two words together, DANGUNWANGGEOM must have been both the master to preside over religious ritual and the ruler..
GOJOSEON was a tribal league composed of walled-towns located between the Taedong River in the south and the Liao River in the north. At the time when Chou Dynasty replaced Eun Dynasty, Chinese history books record that a wise Chinese called "GIJA" came to GOJOSEON. This record gave rise to a story about GIJAJOSEON which meant that GIJA ruled over GOJOSEON. According to the record, MUWANG of Chou Dynasty placed GIJA from Eun Dynasty which had collapsed at his hands into the king of GOJOSEON. Anyway, it is difficult to verify this record for want of empirical data. "JEWANGUNGI" (literally "Records of Previous Kings") depicts GIJA as the king of Late GOJOSEON, and the recorded story was taken for the honour of GOJOSEON among scholar rulers of JOSEON Dynasty which was based on Confucian ideology.
The earliest historical record placed the existence of GOJOSEON before the fourth century B.C. According to another historical record called "Witak," Yen Dynasty under the reign of King So (3ll-270 B.C) was engaged in hegemonic struggle with GOJOSEON. Considering that Yen Dynasty was the dominant power of China, GOJOSEON must have gathered power strong enough to contend with Yen Dynasty.

2) WIMANJOSEON

In the late 4th century B.C, GOJOSEON underwent a sweeping change.
The expanding territory of Yen Dynasty placed it in clash with GOJOSEON. In the clash, GOJOSEON suffered defeat with the resultant shrinkage of its territory, thus forcing it to move its capital to the vicinity of PYEONGYANG.
Toward the end of the 3rd century B.C, China saw Chin Dynasty fall and Han Dynasty rise into a powerful state. The second unification of China was achieved by Han Dynasty, but conflicts with the local lords continued to plague the state. Large numbers of refugees poured into GOJOSEON and there was a Chinese called "Wiman" among the refugees. He is said to have brought about l,000 followers to GOJOSEON. He had his hair knot (the traditional hairstyle) cut off and put on Korean costumes. King Ju of GOJOSEON made him defend the western frontier but Wiman took advantage of this appointment as an opportunity to build his strength. As Han Dynasty invaded GOJOSEON in l94 B.C, Wiman pulled his troops from the western frontier and led them to the capital in a disguised intention to defend it. He proclaimed himself as the King of GOJOSEON and changed GOJOSEON into WIMANJOSEON named after him..
Wiman was a Chinese refugee who became a citizen of GOJOSEON, and WIMANJOSEON he founded was neither a Chinese kingdom nor a Chinese colony, because it was built on the base of GOJOSEON. But his power base was rather precarious, because he was constantly plagued by conflicts between the indigenous settlers and Chinese refugees. In order for him to maintain his fragile power base built on ethnic conflicts, Wiman had to appease the indigenous settlers and enlist their support. There were groups who were identified by "Sang", who were presumed to be the indigenous settlers of GOJOSEON. Wiman's attempt to erase distinction between the different ethnic groups illustrates a contrast to the policy of NAKRANG, a Chinese commandery, which enforced strict discrimination between the indigenous settlers and Chinese. Considered in this vein, WIMANJOSEON may as well be viewed as the continuation of GOJOSEON and not the discontinuation of its history.

3) Establishment of Four Han's Comanderies

WIMANJOSEON gathered its military strength, adopted Chinese culture and institutions and achieved its economic prosperity by playing an intermediary role in trade between China and the other tribal leagues in the south. It conquered its neighbor tribal leagues and enlarged its territory. In the process of territorial expansion, it restored part of the old territory of GOJOSEON then occupied by a Chinese commandery, Imdun. The territorial expansion of WIMANJOSEON imposed a new threat to Han Dynasty which had been plagued by Hsiung Nu nomads pressing down southward. Han Dynasty found itself under a crushing burden of fending off two foreign forces. This put Han Dynasty on alert, enabling it to prepare itself for the worst case of alliance between Hsiung Nu and WIMANJOSEON. The fear of what would befall the Dynasty made MUWANG of Han forestall by launching a massive invasion on land and by sea with 50,000 foot soldiers and 7,000 navy forces. The WIMANJOSEON forces fought heroically for one year, but its strength to resist began to decline after a group of indigenous settlers surrendered and UGEOWANG (a grandson of Wiman) was killed in action. Wanggum Sung, the capital of WIMANJOSEON, came into the grip of the foreign invaders. WIMANJOSEON perished in l08 B.C and this forced a massive flow of population southward.
Han Dynasty established four commanderies in the territory of WIMANJOSEON, NAKRANG, Hyonto, Chinbon, and Imdun, and their exact locations have not been clarified despite a long-drawn scholarly debate. In general, their locations are presumed to lie north of the HANGANG. In 20 years, Han Dynasty abolished the two commanderies, Chinbon and Imdun, and had their territories ruled by NAKRANG and Hyonto. Later, Han removed Hyonto to Manchuria (75 B.C).
The four Chinese commanderies were increasingly threatened by the formation of tribal leagues in the south. One of the last remaining commanderies, NAKRANG, was incorporated into the new emerging Kingdom of GOGURYEO in 3l3. Chinbon was the last to fall by another emerging Kingdom of BAEKJE, thereby terminating the existence of all Chinese commanderies in the Korean peninsula.