Daidō era (806–810) — Japanese nengō and imperial transition

Emperors and succession

During Daidō the throne passed from Emperor Kanmu to his successor, Emperor Heizei, and later to Emperor Saga. Heizei ascended in 806 and abdicated in 809 in favor of Saga, a relatively short reign that reflected patterns of court politics and the occasional use of retirement rather than death to change rulers.

Notable events

• 806: Beginning of the Daidō era and the start of Heizei's reign.
• 809: Abdication of Heizei; accession of Saga.
• 810: The Kusuko incident (an attempt by supporters of the retired Heizei to influence succession and regain power), which tested the authority of the new emperor and the court’s capacity to manage rival factions.

Context and legacy

Although brief, the Daidō period occurred during a formative phase of early Heian court government. The era exemplifies how short reigns, retirements, and power struggles shaped the development of imperial and aristocratic institutions. The events around 809–810 influenced later practices for succession, regency, and the management of retired emperors.

For readers seeking further background on era names and imperial chronology, consult general treatments of the Japanese nengō system and the biographies of the two emperors who define this period: nengō, Heizei, and Saga. Additional chronological placement is available by reference to the preceding Enryaku and following Kōnin eras.