Battle of Seibagaharu

勢場ヶ原の戦い

Ōuchi Clan

Bungo Province

Ōtomo Clan

Date:  4/6 of Tenbun 3 (1534)

Location:  Mount Ōmure in Kitsuki in Bungo Province

Synopsis:  From their base in Suō Province, the Ōuchi clan under Ōuchi Yoshioki wielded influence in the Chūgoku region as well as parts of northern Kyūshū, leading to clashes against the Ōtomo clan of Bungo Province.  In preparation for the advance of Ōuchi forces, the Ōtomo took-up positions on several mountain passes to the province as well as on Mount Ōmure.  After the Ōuchi approached, the Ōtomo rushed down the mountain but lost many men in the ensuing battle.  Ōtomo forces from other positions launched counterattacks that ultimately drove the Ōuchi out of Bungo.

Lord:  Ōuchi Yoshitaka

Commanders:  Sue Okifusa

Forces:  3,000

Losses:  358

Lord:  Ōtomo Yoshiaki

Commanders:  Yoshihiro Ujinao, Sōda Chikakado, Bekki Akitsura

Forces:  2,800

Losses:  273 or 283 (including Yoshihiro Ujinao, Sōda Chikakado)

The Battle of Seibagaharu occurred on 4/6 of Tenbun 3 (1534) in the environs of Mount Ōmure in Kitsuki in Bungo Province in Kyūshū.  The battle was waged between Ōuchi Yoshitaka of Suō Province and Ōtomo Yoshiaki of Bungo.  This was the largest battle between the Ōuchi and Ōtomo clans.  This event is also referred to as the Battle of Ōmuresan which was the location for the base of the Ōuchi army during the conflict.

Prelude

In the early Sengoku period, from their home province of Suō, the influence of the Ōuchi clan extended to many areas including to Buzen and Chikuzen in northern Kyūshū, to Iwami and Aki to the east, and to Chikuzen, Hizen and Chikugo provinces to the west.  Meanwhile, the Ōtomo clan, in their role as the military governors of Bungo Province from long ago, sought to assert their control over northern Kyūshū and viewed the Ōuchi as a provocative actor in their sphere of influence.  From the fifteenth century to the first half of the sixteenth century, small-scale clashes persisted between the Ōtomo and Ōuchi forces in areas centering around Buzen and Chikuzen.  While engaging in battle against the Ōtomo, the Ōuchi also fought against the Shōni clan of Chikugo, strengthening their hegemony in northern Kyūshū.

After his death on 12/20 of Kyōroku 1 (1529), Ōuchi Yoshioki was succeeded by his eldest son, Ōuchi Yoshitaka, whereupon Yoshitaka dispatched his senior retainer, Sue Okifusa, with orders to seize control of the northern portion of Kyūshū.

In 1533, after invading Akizuki in Chikuzen, Okifusa was defeated by forces led by Ōtomo Yoshiaki.  As a result, a large-scale battle between the Ōuchi and the Ōtomo became inevitable.

In 1534, after Okifusa returned to Suō Province, Yoshitaka sent him as the general in charge of a contingent of 3,000 forces to Shimonoseki with the aim of re-entering Kyūshū to pacify Bungo – the home province of the Ōtomo.

Ōtomo Yoshiaki sent an army of 2,800 soldiers under the command of Yoshihiro Ujinao (the lord of Yoshihiro Castle in Kunisaki in the eastern portion of Bungo and Sōda Chikakado to Mount Ōmure in Buzen to oppose the invasion of Bungo by the Ōuchi army.  All together, in the fourth month, 5,800 forces (or 6,100 forces if including those at the Kana Pass) assembled at the provincial border of Bungo and Buzen and the battle began.

Course of events

The Ōtomo positioned 1,000 soldiers on Mount Ōmure, in addition to 1,000 soldiers under Kitsuki Chikazane (the grandfather of Kitsuki Shigehide) and Takita Akinari at the Tateishi Pass linking Buzen and Bungo provinces, and 800 soldiers under Shite Yasuhisa and Nohara Masahisa at the Jizō Pass.  Apart from the main division, Ōkami Shigeuji and Hayashi Shigeharu led a battalion of 300 soldiers to establish a position at the Kana Pass.

The Ōuchi army utilized spies to track the movements of the Ōtomo army, grasp their intentions, and spread false information to sow confusion among the Ōtomo troops.  Upon the recommendation of Sada Tomoyasu, the head of the Sada clan and the Usa District, the Ōuchi traversed the Sada Pass and, in the early morning of 4/6, traveled through Seibagaharu with a plan to launch a surprise attack against the Ōtomo army located on Mount Ōmure.

Hirose Hironori proposed that the Ōtomo urgently hail their forces positioned at the Tateishi and Jizō passes in an effort to rout the Ōuchi as though the enemy forces had rained down from heaven to cause disarray.  Meanwhile, owing to the exhaustion of the enemy forces, Yoshihiro Ujinao concluded that even with fewer men, the Ōtomo could prevail, asserting that it would be cowardly to watch the enemy forces approach.  The forces then rushed down the mountain to charge the Ōuchi troops.  The other troops in the Ōtomo army were then obliged to follow.  In the beginning, the Ōtomo fought well with Sōda Chikakado killing Sugi Shigenobu (Nagato-no-kami) in a one-on-one duel.  However, after the superior number of Ōuchi forces converted to a crane-wing formation and attacked from all directions, the Ōtomo were slaughtered.  Ujinao commanded his troops from the front until his horse was struck by an arrow and fell down, and then he fought on the ground, but was toppled by an arrow.  In hand-to-hand combat, the Ōtomo forces were nearly decimated.  Chikakado and Hirose Hironari attempted to come to the aid of Ujinao but were killed.  The Ōuchi army shouted in celebration of their victory.

The 1,800 soldiers remaining at the Ishitate and Jizō passes counterattacked in a battle of revenge.  Attacks and raids occurred from around 11:00 in the morning.  Most of the attacking forces were local, giving them an edge to cause disarray among the Ōuchi.  Having become complacent after their early success and unable to respond effectively, the Ōuchi forces collapsed and lost many soldiers in battle.  Even their commanding general, Sue Okifusa, sustained injuries.  Having gone from apparent victory to defeat, the Ōuchi retreated along the Yorimo River in the direction of Takata in Bungo, returning to Suō Province via sea route.

The retreat of the Ōuchi army translated to a strategic victory for the Ōtomo army.  However, owing to the loss of two commanding generals, and a collapse of the main division of the Ōtomo, from a strategic perspective, the outcome could also be regarded as a draw.

Consequences

Thereafter, clashes persisted between the two clans, but, in 1538, owing to mediation by Ashikaga Yoshiharu, the twelfth shōgun of the Muromachi bakufu, the two sides settled and, as a result, the attempt by Ōuchi Yoshitaka to pacify Kyūshū stalled.  Meanwhile, the Ōtomo witnessed a resurgence in power.  Despite having lost in the battle, Sue Okifusa was dispatched to Kyūshū on further occasions to fight against the Shōni clan and gōzoku, or wealthy families, from Chikuzen Province, maintaining the trust of Yoshitaka.

This represented the final large-scale battle between the Ōtomo and Ōuchi clans, and, following the settlement, clashes between the clans almost completely ended.  Later, in 1551, Ōuchi Yoshitaka was usurped by his senior retainer, Sue Takafusa (later known as Sue Harukata), and forced to kill himself in an event known as the Tainei Temple Incident.  Afterwards, the Ōtomo clan rapidly gained power while the Ryūzōji clan of Hizen Province who had, for a period, been associated with the Ōuchi, became independent, so the Ōuchi lost almost all of their influence in northern Kyūshū, enabling the Ōtomo to become the dominant power in the region.