As mentioned in another article, Gunma Prefecture has, by far, the largest number of old large-scale burial mounds, namely Kofun, in the Kanto region. In Japan's first history book, Nihon Shoki, as well as in Kojiki, members of a powerful clan "Kamitsu-Keno" are referred as having played major roles in the wars on the Korean Peninsula or the battle against Emishi (1). Their clan name, "Kamitsu-Keno" derives from the area name where they lived and it roughly corresponds to the present Gunma Prefecture.
|(1)||People who lived in the north of Japan who did not obey to the Yamato administration were called "Emishi". Though the same Chinese characters are used they are not identical with "Ezo".|
According to the periodization of the Japanese history, the Yayoi Period lasted from the 5th century BC (2) to the middle of the 3rd century AD. In the Yayoi Period full-scale rice cultivation was introduced in Japan and many small countries were formed. Following the Yayoi period, the Kofun period began, when the Yamato court gradually integrated Japan, whereby the scale and design of tumuli were regulated to express the closeness of people to the Yamato court and the hierarchy among them.
|(2)||In recent years, it has been proposed that the beginning of the Yayoi period should be traced back to the 10th century BC in relation to the evaluation of carbon dating, and discussions continue.|
Since rice cultivation came from the continent, the spread to the eastern part of Japan was delayed. It seems that the rice cultivation first came into the Gunma Prefecture from the Japan Sea coastal area through the present Nagano Prefecture and started as late as in the 2nd century AD at the foot of Mt. Haruna. In those days, people had their dwellings on the plateau and cultivated paddy fields in the nearby valleys. They did not use the large wetlands, which seem to be more suitable for rice cultivation today, because they were not able to control large-scale irrigation.
|Images of two types of front-square kofun|
(Front and rear-square burial mound)
Symbol of anti-Yamato coalition?
(Front-square and rear-rounded burial mound)
The debate continues on whether this phenomenon should be regarded as the influx of culture or whether people flowed in with the culture. In this connection, it is interesting to note, Nihon Shoki reports that the tenth Emperor Sujin ordered his prince "Toyoki Irihiko" to rule the eastern country and his descendants became Kamitsu-Keno clan. On the other hand, some people believe that the reason why the front and rear-square burial mounds were first adopted as the standard for large burial mounds is that it was a common denominator of the countries under the influence of the Yamato's opponent "Kunu" which should have existed in the Tokai region.
The Ota Tenjin-yama Kofun, which is thought to have been built in Ota City in the eastern part of Gunma Prefecture in the first half of the 5th century, is a 210-meter-long front-square and rear-rounded Kofun and is the largest of this type in East Japan. After that, the Keno clan seems to have been split into two groups: Kamitsu-Keno in the present Gunma and Shimotsu-Keno in the present Tochigi. A large-scale tumulus comparable with the Ota Tenjin-yama Kofun was never built again.
According to the view of archaeologist Toru Wakasa, Ota Tenjin-yama Kofun adopted the design of the tumuli of the Furuichi Kofun cluster in Habikino City, Osaka Prefecture and is half the size of the largest of the cluster, the Emperor Oujin's tumulus. After Ota Tenjin-yama Kofun, this design became the standard adopted by the chiefs in the region who insisted to be the legitimate successors of the legendary founder of the clan. So, the tumuli of the Iwahana Kofun cluster on the bank of the region's main stream Ino-River all follow the same design in the smaller scale. Their successors, the tumuli of the Hodota Kofun cluster, which are located along the Ino-river upwards, also adopted the same design. Finally, the same standard was applied to the Watanuki Kan-non-yama Kofun, which was built in a corner of the Iwahana Kofun cluster in the latter half of the 6th century. The relocation of the tomb sites took place within the Ino River basin, which was the territory covered by the chiefs buried in those Kofun.