Kokubun Tanenaga (国分胤長)

Tanenaga KOKUBUN (c. 1178 to June 3, 1200) is a samurai, who is said to have been in Miyagi County, Mutsu Province during the Kamakura period. He is said to have been a son of Tanemichi KOKUBUN, but there is a possibility that he may not have existed.

The Kokubun clan (in Mutsu Province) is samurai, who had possessed the southern part of Miyagi County, Mutsu Province from the period of the Northern and Southern Courts to the Sengoku period (period of warring states). It is said that the origin of the clan can be traced back to the time when Tanemichi KOKUBUN from Shimousa Province moved to Kokubun-no-sho (国分荘), Miyagi County, which was given to him as reward grants for the Battle of Oshu. According to the family tree edited by Yoshikazu (義和) SAKUMA in Sendai Domain, Tanenaga KOKUBUN was the first son of Tanemichi KOKUBUN, and his mother was a daughter of Tsunenobua USUI (臼井常信). He had two younger brothers, Tanekiyo (胤清) and Michiuji (道氏), and an older sister and a younger sister, who got married to Tanehide OSUGA (大須賀胤秀) and Hideyuki (秀行) USUI respectively. It is said that he married a daughter of Taneyori TO, a younger brother of Tanemichi, and had a son named Kokujumaru (国寿丸), who grew up to be Tanemochi KOKUBUN.

According to the family tree edited by Sakuma, Tanenaga died at the age of 23 on June 3, 1200, which means he was born in 1178. Although his younger brother Tanekiyo (胤清) died at the age of 16, his youngest brother Michiuji lived long, and was allowed to possess an estate in Yamaoka-no-sho, Inba County, Shimousa Province.

The family tree edited by Sakuma shows that the mainstream of the Kokubun clan originated in Mutsu Province started with Tanemichi and succeeded by Tanemochi, however, these names are not referred to neither in the family tree prepared in Shimousa Province nor in the family tree owned by the Furuuchi clan in Mutsu Province. In several materials and family trees edited in Sendai Domain in the Edo period, Tanemichi is regarded as the ancestor of the Kokubun clan in Mutsu Province, however, this is the only common infomation in the earlier records, and other information related to the Kokubu clan until the Sengoku period (period of warring states) widely varies. Therefore, it is also said that it was the family tree editor who associated Tanemichi with the Kokubun clan in Mutsu Province. Even if we take the view that the relocation from Shimousa to Mutsu was factual, individual names mentioned in the family trees are not reliable, and the existence of Tanenaga remains doubtful.