Jinshin incident

The Jinshin War (壬申の乱, jinshin no ran) was a succession dispute in Japan which broke out in 672 following the death of Emperor Tenji. The name refers to the jinshin (壬申) or ninth year of the sixty-year Jikkan Jūnishi calendrical cycle, corresponding to the Western year 673.

Tenji had originally designated his brother, Prince Ōama, as his successor, but later changed his mind in favor of his son, Prince Ōtomo. In the course of the violence that erupted as a result of factional rivalries, Ōtomo, having taken the throne as Emperor, took his own life after reigning for less than a year. His uncle Ōama then succeeded to the throne as the Emperor Tenmu.

Emperor Tenji ascended to the throne and set up a capital at Ōmi-Ōtsu (currently Ōtsu city, Shiga Prefecture). He made his best efforts for the foundation of a strong country, imitating the Tang Dynasty in China, importing the Tangs' culture, architecture and political systems. Japan had to pretend to have as much power as Tang because if Japan were regarded as weak, it was feared that the Tang might invade and conquer the country.

The next thing Tenji needed to do was to secure his successor. His Empress-consort was Yamato-hime but there were no children between the two. He had to find the right man from the sons of non-Imperial wives. Prince Takeru was the first son but he was mute by nature and died when he was seven years old. Prince Ōtomo was the next prince of the Emperor. He was a hard worker, and was very clever and intellectual. He had enough ability to be the next Emperor.

Although Ōtomo was almost perfect, his mother was of low birth. She was from the rural area landlord's family and was not Imperial-Household-born. This was a great disadvantage in considering Ōtomo to ascend to the throne.

At the same time, a younger brother of the Emperor Tenji's was as excellent as Ōtomo. He, Prince Ōama, had almost the same fitness as the Emperor, except that he was younger. His reputation was much greater than Ōtomo because he was of higher birth and was more suitable to be the next Emperor. This was a major cause of the trouble to come.

In 670, the Emperor Tenji got sick. He realized that he couldn't live long, and he wished that, after his death, the Imperial Dynasty would pass to his son, Prince Ōtomo. Because Ōtomo's greatest rival was Ōama, the Emperor attempted to drive Ōama away. He invited the prince to his bedroom and asked if Ōama had an intention to take the throne. If Ōama answered yes, the Emperor would have arrested and punished him as a traitor. Prince Ōama was clever enough to know his trick and answered that he had no will to succeed the throne and he wanted Ōtomo to be the next Emperor. He added that he wanted to be a monk instead of inheriting the throne and would retire to a temple in Yoshino. Because there were no reasons to punish Ōama any longer, the Emperor accepted the prince's proposal. Ōama went down to Yoshino the next day and became a monk.

...
Wikipedia