This re-relocation was said to have been caused by a sequence of events, from the assassination of FUJIWARA no Tanetsugu which occurred in Nagaoka-Kyo, to the disinheritance of Imperial Prince Sawara, which also delayed the building of Nagaoka-Kyo and as a result it did not make much progress.
この再遷都は、長岡京で興った藤原種継暗殺から早良親王廃太子に至る一連の騒動や、長岡京の造営がなかなか進まなかったことが影響しているとみられている。