Emperor Go-Reizei (1025–1068), whose reign name literally means "Emperor Cool Fountain the Second," was the 70th emperor of Japan according to the traditional chronology, reigning from 1045 to 1068.
Born Prince Chikahito, Go-Reizei was the eldest son of the Emperor Go-Suzaku and Fujiwara Kishi, a daughter of Fujiwara Michinaga. Go-Reizei ascended to the throne at a time when the Fujiwara family dominated the Imperial court, thanks to their success at bearing many daughters and then marrying them to Imperial princes. Since medieval Japanese society was uxorilocal, meaning that married couples lived in the household of the wife's father, this meant that future Japanese emperors would grow up in the household of their maternal grandfather - a Fujiwara - and would thus be under his sway once they took the throne, which the Fujiwara typically made sure was while they were still children. As soon as an emperor got too old, the Fujiwara lord would force them to abdicate in favor of another Imperial prince who was also the son of a Fujiwara daughter.
This system worked for many hundreds of years, allowing the Fujiwara to rule Japan through a long succession of puppet child emperors, but the Fujiwara's luck came to an end during the reign of Go-Reizei. Go-Reizei was already a sub-optimal choice, being that he was already 20-years old when he took the throne, but the Fujiwara princesses had been having trouble bearing sons of late, and there were no other child princes ready to take the throne. Then, although Go-Reizei was dutifully married off to two Fujiwara princesses, neither one could produce an heir, whether as a result of impotence, infertility, inbreeding, or sheer bad luck, and Go-Reizei reigned for more than 20 years before dying childless at the age of 44. This allowed an emperor who was both an adult and not the son of a Fujiwara princess - Go-Sanjō - to take the throne, marking the end of Fujiwara rule over Japan.
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