Civil war breaks out! Prince Otomo vs. Prince Oama

In 671, Emperor Tenji named Prince Otomo who was his favorite son by a beloved courtesan, to the office of chancellor, the highest ministerial post of all. Under terms of the new administrative code, a chancellor had to be an imperial son acting as regent (sessho) for the emperor, so this appointment was in effect an announcement that Prince Otomo was to succeed the emperor, instead of the crown prince Prince Oama. This was an unexpected turn of events as the crown prince (who was the younger brother of Tenji) had been appointed by the court as successor earlier in 664. It may be supposed that the disappointment and discontentment felt by the crown prince led to the scene reportedly created by the crown prince at a party given in the new Otsu palace during 668 … the crown prince is said to have seized a spear, suddenly ramming it into the floor.

After Emperor Tenji’s death, a struggle for the succession to the Imperial Throne occurred between Prince Otomo and Tenji’s younger brother Prince Oama (who later became Emperor Temmu).

War broke out in the six month of 672 (according to Nihon shoki) when Prince Oama, believing that a plot was afoot at the Omi court against him, issued orders to mobilize troops based in his Yuno estate in the district of Ahachima as well as those of provincial governors. The outcome of the war would depend on who could obtain the support of leaders in Japan’s eastern and northern provinces, so Prince Oama and his sons moved quickly by heading off across the mountains to the eastern provinces of Iga and Ise.

Meanwhile, Prince Otomo headed out to obtain military support from leaders in the west and south, but his plans were fouled as the governors of Kibi and Tsukushi refused to cooperate.

Prince Oama meanwhile had a difficult task as he was aided by only small bands of soldiers. However, he was aided by the governor of Ise Province who sent 500 soldiers to close the Suzuka pass so that he could not be pursued from the capital. Eventually, he was able to defeat Prince Otomo by mustering two armies: one that crossed the mountains from Ise into Yamato and the other that advanced down the Fuwa road toward the capital. With those two armies, Prince Oama won his decisive victory.

Prince Otomo committed suicide while his minister of the right was executed, his heirs and supporters sent into exile.

Following the civil war (which is known today as the Jinshin conflict of 672) and the end of Emperor Tenji’s reign, Prince Oama ascended the throne as Emperor Temmu. In 673,  Emperor Temmu moved the capital back from Otsu back to the Yamato province, on the Kiyomihara Plain. He named his new capital Asuka, and reigned from his new imperial palace Kiyomihara Miya in Asuka.

The Manyoshu includes a poem written soon after the end of Jinshin conflict of 672 that refers to Emperor Temmu’s capital:

Our Sovereign, a god

Has made an Imperial City,

Out of the stretch of swamps,

Where chestnut horses sank,

Their bellies.

— Otomo Miyuki

***

References:

Nippon Gakujutsu Shinkokai (1969) The Manyoshu p. 60.