Battle of Mimigawa

What Happened

In 1578 the armies of the Ōtomo clan (大友氏, Ōtomo-shi) and the Shimazu clan (島津氏, Shimazu-shi) met at the Mimi River in what is now Miyazaki Prefecture, on the eastern side of Kyushu. The Ōtomo host was commanded in the field by Tawara Chikataka (田原親賢), a brother-in-law of the clan head Ōtomo Sōrin (大友宗麟). The Shimazu side was led by Shimazu Yoshihisa (島津義久), the eldest of the four Shimazu brothers who were then consolidating their hold on southern Kyushu.

The fighting took place around Niiniin Taka Castle (新納院高城, Niiniin Taka-jō), a fortress on the Shimazu side of the river. The Ōtomo force crossed the Mimi River to press the attack. The Shimazu defenders held, and the Ōtomo army was broken in the fighting that followed. The engagement is dated to Tenshō 6 (天正六年), the sixth year of the Tenshō era, which ran from 1573 to 1592.

Background

The battle belongs to the Sengoku period (戦国時代, Sengoku jidai), the century and a half of near-continuous regional warfare that ran from the middle of the fifteenth century until the country was reunified at the end of the sixteenth. It falls specifically within the Azuchi–Momoyama period (安土桃山時代, Azuchi–Momoyama jidai), the stretch from 1573 to 1603 named after the castles of Oda Nobunaga and Toyotomi Hideyoshi.

Through the 1570s the Shimazu were pushing north out of their home province of Satsuma, absorbing or destroying the smaller houses of southern Kyushu one by one. The Ōtomo, based in Bungo in the north-east of the island, were the great rival power of Kyushu and had no intention of letting the Shimazu swallow the island unopposed. The Mimi River campaign was the Ōtomo attempt to check that advance. Ōtomo Sōrin, who had converted to Christianity and taken the baptismal name Francisco, committed a large army to the venture; command in the field was delegated to Tawara Chikataka.

Why It Mattered

The defeat at the Mimi River was a strategic catastrophe for the Ōtomo. A clan that had been one of the most powerful houses in Kyushu lost the initiative in the south and never recovered it. The Shimazu were left free to continue their campaign of unification across the island, and their momentum carried them through the remaining Kyushu houses over the following decade.

The battle is also remembered as a demonstration of Shimazu tactics. Shimazu Yoshihisa and his brothers — Yoshihiro, Toshihisa and Iehisa — fought as a coordinated team, and the victory at the Mimi River became one of the founding feats of the Shimazu legend. Shimazu Iehisa (島津家久) is associated with the conflict in the records of the campaign. For the Ōtomo, the loss marked the beginning of a decline that would see their domains reduced and their independence ended within a decade.

The Name in Japanese

The battle is written 耳川の戦い and read みみかわのたたかい (mimikawa no tatakai).

• 耳 — read みみ (mimi) here. It means "ear". On its own this is the ordinary Japanese word for the ear, and it is the first element of the river's name.
• 川 — read かわ (kawa) here. It means "river". Note that when 川 follows another element in a compound the reading is usually the native Japanese kawa; the Sino-Japanese reading sen appears in names like 河川 (かせん, kasen), "rivers", but not in this river name.
• の — read の (no). The possessive/linking particle, written in kana. It joins "Mimi River" to "battle": literally "the battle of the Mimi River".
• 戦 — read たたかい (tatakai) here. It means "battle" or "fight". This is the kun'yomi, the native Japanese reading, of a character whose Sino-Japanese reading is sen, as in 戦国 (せんごく, sengoku), "warring states". The verb behind it is 戦う (たたかう, tatakau), "to fight".
• い — read い (i). Written in kana; it completes the noun form 戦い (tatakai).

So the name breaks down as 耳 (mimi, "ear") + 川 (kawa, "river") + の (no, linking particle) + 戦い (tatakai, "battle"): "the Battle of the Mimi River". A useful pattern for readers of Japanese history: river battles are almost always named with this 〜川の戦い formula, as in 川中島の戦い (Kawanakajima no tatakai), the battles of Kawanakajima.

Key Figures

Shimazu Yoshihisa (島津義久) — head of the Shimazu clan and commander of the victorious army at the Mimi River. The eldest of four brothers who together directed the Shimazu drive to dominate Kyushu.

Ōtomo Sōrin (大友宗麟) — head of the Ōtomo clan, based in Bungo in northern Kyushu. A Christian convert, he committed his house to the campaign against the Shimazu that ended in defeat at the Mimi River.

Tawara Chikataka (田原親賢) — Sōrin's brother-in-law and the commander of the Ōtomo force in the field at the Mimi River.

Shimazu Iehisa (島津家久) — a Shimazu commander associated with the conflict. One of the four Shimazu brothers whose campaigns broke Ōtomo power in Kyushu.