Hikami no Kawatsugus War (a political event in Nara period) (氷上川継の乱)
In 770, Shirakabe no okimi (Prince Shirakabe), the grandchild of Emperor Tenchi, was enthroned (as Emperor Konin) after Emperor Shotoku died. A descendant of Emperor Tenmu inherited the imperial throne after Jinshin War, however, many Imperial Family members from the Imperial line of Emperor Tenmu were either killed or punished due to continuous political changes during the Nara period. Therefore, mainstream factions of the Imperial line from Emperor Tenmu died out after the death of Emperor Shotoku, leading to the revival of the Imperial of Tenji.
HIKAMI no Kawatsugu was the child of Shioyaki no okimi (Prince Shioyaki or HIKAMI no Shioyaki) and Imperial Princess Fuwa (the Imperial princess of Emperor Shomu) and was also the great-grandchild of Emperor Tenmu, however, Hikami was dethroned due to the execution of Shioyaki no okimi from his involvement in FUJIWARA no Nakamaro's War. Many believed that Kawatsugu, whose parents were both from the Imperial line of Emperor Tenmu, should be the legitimate succession to the Imperial Throne.
In 781, Emperor Konin enthroned Imperial Prince Yamabe, the Crowned Prince. Thus, the enthronement of Emperor Kanmu was accomplished. In February, 782, the following year of the enthronement, YAMATO no Otohito, a shijin (a lower rank officer of the Imperial or noble families, used as a guard or miscellaneous serviceman) of Kawatsugu, was captured after he entered the palace wearing weapons. During the hearing, Otohito confessed about the rebellion planned by Kawatsugu. His confession revealed Kawatsugu's plan to gather a group of people to break into the palace from Hokumon (the North gate), and overthrow the Imperial Court in the evening of March 2. Immediately after the confession, the Imperial envoy was sent to capture Kawatsugu, however, Kawatsugu was already gone. On March 14, the same month, Kawatsugu was captured while he was hiding in Katsujo County, Yamato Province.
Even though the crime that Kawatsugu committed was deserving of the punishment of death, he instead received a lower punishment and was exiled to Izu Province. His mother, Imperial Princess Fuwa, and his sisters were exiled to Awaji Province. As a result of being implicated in the incident, Sangi (a councilor) FUJIWARA no Hamanari (the Capital House of the Fujiwara clan), his father-in-law, was demoted to the Dazai no ingai no sochi (an outer official of the Dazaifu) and the Capital House collapsed at only the second generation. Furthermore, YAMANOUE no Funanushi, Mikata no okimi, Sangi OTOMO no Yakamochi, Ueji no kami (Captain of the Right Division of Outer Palace Guards) SAKANOUE no Karitamaro were also punished. (Yakamochi and Karitamaro cleared their suspicions and regained to their ranks).
In June of the same year, Udaijin (minister of the right) FUJIWARA no Uona was discharged from his office. There is no record about Uona's crime in "Shoku Nihongi," however, it is thought that he was implicated in Kawatsugu's incident.
After this incident, the Imperial family from Emperor Tenmu line was completely removed from the succession of the Imperial Throne.
In 806, after the death of Emperor Kenmu, the crime of Kawatsugu was forgiven and he returned to Jugoinoge (Junior Fifth Rank, Lower Grade).