Goseong Songhak-dong Tumuli and Gojaguk
Sogaya(small state), along with Ara-Gaya was a major political force that formed the federation of Gaya states (A.D. 350 – A.D. 562). To this day, most researchers as well as public believed that the territory of Sogaya was the area around today’s Goseong in Gyeongsangnam-do.
However, Sogaya was most likely the term that referred to many tribal states that existed in the western part of today’s Gyeongsangnam-do area, including Goseong.
The result of recent archeological researches shows that the western part of Gyeongsangnam-do area exhibits a significant level of spiritual and physical homogeneity in terms of forms of pottery, tombs and funeral rituals. However, it is not plausible to think that Goseong was a center of development of such a wide cultural band. The distribution of tombs indicates that many small states existed around several areas that include Goseong, Jinju and Sancheong. It appears that these small states occupied a common cultural band.
Pottery culture unique to Sogaya began to form around A.D. 5th century and geographic characteristics become prominent as time passed. During the growth period, production and distribution of Sogaya’s potteries took place in many regions: the Nam-gang river area including Sancheong and Jinju; the southern sea coast area including Goseong, Tongyoung, Sacheon and Hadong Based on pottery forms, tomb style and distribution of tombs, the development of Gojaguk could be described in terms of three stages: foundation period (A.D ～350), period of growth (A.D 350～525), period of decline (A.D 525～560) In terms of tomb style of Gojaguk, wooden coffin tombs are built during the 4th and the early 5th century, which are replaced by stone coffin tombs by the middle of the 5th century. Then, beginning in the 6th century, stone chamber tombs began to spread widely, starting with the upper class people.
People who built Songhak-dong tumuli in Goseong is considered a leader of Sogaya from the late 5th to early 6th century. It is speculated that Gojaguk rapidly grew as it traded with other Gaya states, Baekje and Japan beginning in the late 5th century, which is proven by the distribution of potteries of Sogaya.
After the mid-6th century, Baekja and Shilla began to encroach upon Gaya region, which led to the fall of Gojaguk, the fall of Gojaguk is speculated to be around A.D. 560.