Kōgyoku was not only the second woman to ascend to Japan‘s chrysanthemum throne, but also the third.
Born Princess Takara, she was the great-great granddaughter of Emperor Bidatsu, and great-great grandniece to Empress Suiko – the first woman to rule Japan. She married her uncle, Emperor Jomei, and became his consort, bearing him three children.
When Jomei died in his late forties, it was Takara who succeeded him, rather than their teenaged son, Naka no Ōe. She took the name Kōgyoku and the title Sumeramikoto or Amenoshita Shiroshimesu Ōkimi (治天下大王), meaning “the great queen who rules all under heaven”. The throne was not stable, however, and Kōgyoku’s reign was beset by challenges from the powerful Soga clan.
To prevent them from seizing total power, Naka no Ōe and his friends staged a coup intended to destroy the most powerful branch of the Soga family, which was led by statesman Soga no Iruka . In July of 645, during a ceremony in the throne room, Naka no Ōe assassinated Soga no Iruka, right in front of his mother.
Kōgyoku was deeply shocked by the violence she had witnessed (later known as the Isshi Incident), and more than that, at the time it was believed that being present at a murder polluted the soul. No longer considering herself fit to rule, Kōgyoku wished to abdicate immediately in favour of her son. She was instead convinced to pass her title to her brother, who became Emperor Kōtoku.
Kōtoku ruled from 645 – 654 and died without a living heir. In 655, Kōgyoku re-ascended to the throne under the new name of Empress Saimei. As Saimei she ruled for seven more years, before dying on a military expedition to Korea.
Women’s Studies Encyclopedia, Volume 2 – Helen Tierney
Japan Encyclopedia – Louis-Frédéric, Käthe Roth