Yōmei no Suemasa (陽曰月の末政, 561/562 – Winter 640) was a pre-eminent ōomi (regional governor) and later Dai-ryōshu (“Great Lord of the Realm”) in Asuka period Japan. One of the few well-documented Japanese figures from the period, Suemasa played a pivotal role in the establishment of centralised governance in Japan, and was often romanticized throughout the following centuries.

Early Life

Originally named Asuka no Naohei (飛烏の直平), Suemasa was born to an Agatanushi family in modern Nara Prefecture. It was during the Sakurai Rebellion (sometimes referred to as the “Years of the Three Flowers”) that Suemasa pledged himself to Emperor Yōmei and won a great victory at the Battle of Nakamashi against the forces of the incumbent Emperor Sushun. When his superior, Niwa no Fusahiko failed to reach the intended site in time, Suemasa led a vanguard of 600 troops and feigned a retreat across a small stream. When the opposing forces followed, Suemasa attacked “with the ferocity of a tiger” and routed the enemy. He then brought the head of the commander, Okaba no Akimasa to Empero Yōmei. Fusahiko attempted to downplay his inferior’s success by reprimanding him for his lack of patience, to which Suemasa retorted “a man needs patience only when hunting hares”. Impressed by his bravery, Emperor Yōmei named Suemasa the muraji of Nara in place of Fusahiko. Disgraced, Fusahiko fled west to the court of Konoe no Takeyuki, who had named himself Emperor Jinsei.

War against Sushun

Asuka no Naohei was no longer a name worthy of one of the most powerful men in Japan, and thus Emperor Yōmei granted the name of Nara no Naohei (奈良の直平), however, Naohei requested that he be granted the name of Suemasa, thus abandoning his lowly past. Suemasa set about rallying Emperor Yōmei’s forces in order to face the remainder of Emperor Sushun’s supporters. He also began constructing vital roadworks and canal systems throughout Nara, including structures he called Kōtei no tō (皇帝の塔) or “Emperor’s Towers” to enforce Yōmei’s authority upon the clans. In 587, Suemasa attacked Sushun’s forces at Shakujo Lake, winning another great victory before advancing upon his capital at Tsu. Sushun quickly surrendered after seeing Suemasa’s army.

With Sushun dealt with, Suemasa turned back to face Konoe no Takeyuki who had used Suemasa’s absence to expand his territory north into Kawachi Province, directly threatening Kyoto. Suemasa managed to push back Takeyuki’s forces, but spent two years reinforcing various hill forts and reasserting Emperor Yōmei’s authority over Nara. However, during this time, Yōmei died aged 69. Suemasa then dedicated himself to Yōmei's son, Shōtoku who was a teenager at the time. Shōtoku's ardent Buddhist beliefs apparently were at odds with Suemasa's Shinto faith but nonetheless, Suemasa chose to support the young emperor.

War against Jinsei

By the summer of 589, Suemasa was back in the field and defeated Kaneyuki in a series of minor skirmishes along the Kinokawa River, pushing his forces back to Wakayama.

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