著者

西本 昌弘

出版者

国立歴史民俗博物館

雑誌

国立歴史民俗博物館研究報告 (ISSN:02867400)

巻号頁・発行日

vol.134, pp.75-91[含 英語文要旨], 2007-03

---

薬子の変については、藤原薬子・仲成の役割を重視してきた旧説に対して、近年では平城上皇の主体性を評価する見方が定着しつつある。これに伴い、「薬子の変」ではなく、「平城太上天皇の変」と呼称すべきであるとの意見も強くなってきた。しかし、平城上皇の主体性を強調することと、薬子・仲成の動きを重視することとは、必ずしも矛盾するものではない。私は前稿において、皇位継承に関する桓武の遺勅が存在した可能性を指摘し、平城上皇による神野親王廃太子計画について考察を加えた。私見によると、薬子の変もこの桓武の遺勅を前提とする神野廃太子計画と一連の動きのなかで理解することができると思われる。そこで研究史を振り返りながら、平城・嵯峨両派官人の動向に再検討を加え、薬子の変にいたる原因と背景について考察した。本稿の結論は以下の通りである。桓武天皇は死去のさいに、安殿・神野・大伴の三親王が各一〇ヶ年ずつ統治すべきことを遺勅したが、平城はこれを破って、第三子の高岳親王を皇位につけようとし、神野親王の廃太子を計画した。薬子の変の遠因は神野廃太子計画にも通じるこの皇位継承問題であり、平城の即位前後から平城派と嵯峨派の両派官人の対立ははじまっていたとみられる。神野の廃太子に失敗した平城は、三年ほどの治世で譲位した。これは嵯峨が一〇ヶ年統治したのち平城が数年間復位して、高岳への皇位継承をより確実にしようとの意図からであった。しかし、嵯峨が平城のこの提案を拒絶したため、平城は譲位したことを後悔しはじめ、嵯峨側との対立をさらに深めていった。薬子の変の直前には、平城派の官人が衛府や要衝国の国司に任じ、かつて北陸道観察使であった藤原仲成らが越前方面などで平城派の勢力拡大に努めていた。このため嵯峨側は弘仁元年(八一〇)九月、平城派官人の衛府や国司の任を解き、彼らを辺遠国に左遷するとともに、自派の官人で衛府と要衝国を固めた。また伊勢・近江・美濃三国の国府と故関に遣使して鎮固し、平城側の蜂起を未然に防ぐことに成功した。薬子の変では越前・近江・伊勢方面に勢力を扶植した仲成の活動が突出しており、平城の藩邸の旧臣の多くは平城に同調しなかった。変における平城上皇の主体性は否定できないが、薬子らの父種継の復権・顕彰が図られた事実や、薬子・仲成の係累が乱後も長く許されなかった事実を勘案すると、薬子・仲成がやはり中心的な役割を果たしていたことを認めない訳にはゆかない。平城上皇や薬子・仲成にとって、王都・王統に関する桓武の構想は否定すべきものであり、それゆえその遺命を無視して、高岳立太子を実現し、平城遷都を計画したのである。薬子の変は桓武の構想を肯定するか否定するかの戦いであったといえる。In recent years, it has become accepted that retired emperor Heizei played a major role in the Kusuko Incident, which is at odds with the old theory that emphasized the roles played by Fujiwara no Kusuko and Fujiwara no Nakanari. This has even been accompanied by vociferous claims that the name of the incident should be changed from the "Kusuko Incident" to the "Retired Emperor Heizei Incident". However, stressing that Emperor Heizei played an active role and attaching importance to the actions of Kusuko and Nakanari are not necessarily contradictory. In a previous paper the author suggested that it is possible that Emperor Kammu had left a will concerning accession to the throne. The author also examined retired Emperor Heizei's plan for getting rid of Crown Prince Kamino. It is the author's opinion that the Kusuko Incident can be understood within the context of a series of events as well as the plot to remove Crown Prince Kamino, which was premised on Emperor Kammu's will.The author examined the factors that led to the Kusuko Incident and their background by looking back at the history of research on this topic and conducting a further investigation of the movements of both the faction of officials aligned with Heizei and the faction of officials aligned with Saga.When he died, Emperor Kammu willed that the three princes Ate, Kamino and Otomo should each reign for ten years. However, Emperor Heizei failed to observe this and sought to put his third son Takaoka on the throne, thereby plotting to stop Prince Kamino from becoming Crown Prince. Consequently, a remote cause of the Kusuko Incident was this problem of succession to the imperial throne, which was also related to the plan to remove Crown Prince Kamino. The confrontation between the Heizei faction and Saga faction of officials had apparently begun around the time Heizei ascended to the throne.Emperor Heizei, who had failed in his bid to remove Crown Prince Kamino, retired after reigning for about three years. He did so intending to restore himself to the throne for several years after Emperor Saga had reigned for ten years so that he could then ensure that Prince Takaoka became emperor. However, because Saga thwarted Heizei's plan, Heizei began to regret his retirement and intensified hostilities with the Saga camp.Immediately prior to the Kusuko Incident, officials from the Heizei faction were appointed as commander of the national military forces and as regional administrator of the region adjoining the capital. Together with his men, Fujiwara no Nakanari, who had at one time had been administrator of a wide area in Hokurikido, strove to increase the influence of the Heizei faction in Echizen and other areas. As a result, in September 810 the Saga camp stripped Heizei-faction officials of military and political duties, and as well as demoting them to provinces near the capital placed officials from their own faction in the positions of national military commander and regional administrator of the region adjoining the capital. In addition, by blockading the three provincial governments of Ise, Omi and Mino and former checkpoints, they succeeded in preventing an uprising by the Heizei camp.The activities of Nakanari, who had continued his influence in Echizen, Omi and Ise, played a prominent role in the Kusuko Incident and many of Heizei's attendants from the time when he had been Crown Prince did not sympathize with Heizei. It cannot be denied that Emperor Heizei played an active role in the Kusuko Incident. However, if we take into account the fact that an attempt was made to reinstate Kusuko's father Tanetsugu and the fact that Kusuko and Nakanari's sons were not forgiven long after the incident, we must acknowledge that Kusuko and Nakanari did indeed play a central role.Emperor Heizei, Kusuko and Nakanari believed that Kammu's ideas on the imperial capital and throne should be denied, and it was for this reason that they ignored the late emperor's instructions and made Prince Takaoka Crown Prince and planned to return the imperial capital to Heijo. In conclusion, the Kusuko Incident was a battle over whether to affirm or deny Kammu's ideas.