Subjugation of Bōchō


Ōuchi Clan

Suō Province

Nagato Province

Mōri Clan

Date:  10/12 of Tenbun 24 (1555) to 4/3 of Kōji 3 (1557)

Location:  Suō and Nagato provinces in the western region

Outcome:  Mōri Motonari succeeded in executing a plan over a period of more than 1.5 years to eliminate the rival Ōuchi clan and to subjugate the Ōuchi territory of Suō and Nagato provinces (although resistance lingered from former retainers of the Ōuchi for over ten years thereafter)

Commanders:  Ōuchi Yoshinaga, Naitō Takayo, Sugi Takayasu, Era Katanobu, Yamasaki Okimori, Nogami Fusatada

Forces:  Unknown

Casualties:  Figures unknown, but Ōuchi Yoshinaga, the seventeenth head of the clan, was forced to kill himself

Commanders:  Mōri Motonari, Mōri Takamoto, Kobayakawa Takakage, Yoshimi Masayori

Forces:  Unknown

Casualties:  Unknown

The Subjugation of Bōchō occurred from 10/12 of Tenbun 24 (1555) until 4/3 of Kōji 3 (1557).  In this conflict, Mōri Motonari, the sengoku daimyō from Aki Province, invaded the territory of the Ōuchi clan in Suō and Nagato provinces.


In the fifth month of 1554, in an event known as the Separation of Suō and Aki, Mōri Motonari severed relations with Sue Harukata and Ōuchi Yoshinaga of Suō Province.  In the tenth month of 1555, at the Battle of Itsukushima, Motonari defeated the main force of the Ōuchi army led by Harukata.  This victory provided Motonari the momentum to plan an invasion of Suō and Nagato provinces.  To begin, on 10/12 of 1555, he moved to a base in Ogata on the border of Aki and Suō to devise his strategy.

In anticipation of an invasion, the Ōuchi army prepared for a counterattack against the Mōri.  The Ōuchi forces included 3,000 soldiers led by Ōuchi Yoshinaga and Naitō Takayo at their home base in Yamaguchi, in addition to defenses on the route to Yamaguchi with Suginomori Takayasu at Rengeyama Castle, Sugi Sōzan and Sugi Takayasu (father and son) at Kurakakeyama Castle, Era Katanobu and Yamasaki Okimori at Susumanuma Castle, Sue Nagafusa (the eldest son of Sue Kataharu) at Tonda-Wakayama Castle, and Migita Takakazu at Migitagatake Castle.  In addition, forces under Nogami Fusatada were stationed at Watarigawa Castle in Nagato Province to keep watch over Yoshimi Masayori at Sanbonmatsu Castle in Iwami Province.

Invasion of the eastern portions of Suō Province

Inducement of surrender and an assault on Kurakakeyama Castle

Beginning in the autumn of 1555, Motonari first aimed to cause instability within the Ōuchi camp.  Suginomori Takayasu at Rengeyama Castle quickly surrendered on 10/18 via a letter to the Mōri.  Upon hearing this news, Sugi Takayasu from nearby Kurakakeyama Castle followed suit and capitulated.  Nevertheless, in light of poor relations between Suginomori Takayasu and Sugi Takayasu, Suginomori Takayasu provided evidence to Motonari that the surrender by Sugi Takayasu was a lie (although it is not certain whether the surrender was a lie), causing a rupture in relations between the Mōri army and Sugi Takayasu.

On 10/9, a Mōri army of 7,000 soldiers (according to some accounts, 20,000 men) commenced attacks, while a Sugi army of 2,600 soldiers sought to intercept them.  The Sugi army included a division of 1,000 men protecting the inner citadel and 800 men in the secondary citadel at Kurakakeyama Castle.  To the east of the castle, 400 men each were positioned at Yatsugahara and Ichigashira.  Despite valiant efforts by the Sugi forces, the Mōri army stormed Kurakakeyama Castle from the rear gate on 10/14 and before dawn on 10/27, killing 1,300 defenders (among them, 800 bushi) along with Sugi Sōzan and Sugi Takayasu (father and son), toppling the castle.

Pacification of the Kuga and Ōshima districts

In the eleventh month of 1555, the Murakami navy allied with the Mōri attacked Ukashima in the Ōshima District and decimated the Ukashima navy allied with the Ōuchi.  Elimination of the Ukashima navy was so extensive that the island had no inhabitants for a period of time thereafter.  By the beginning of 1556, many of the jizamurai, or local fighters, in the Kuga District pledged allegiance to the Mōri, but villagers from the Yamashiro region holed up in Jōkunji Castle in a mountainous area to resist the Mōri.  Saka Motosuke, based in Takamori Castle, was assigned responsibility to pacify the Yamashiro region.  The Mōri army departed from this base to attack and topple Jōkunji Castle around 2/12.  On 2/18, the forces proceeded to attack Ōuchi Yoshinaga along the Mitsuse River.

Around this time, forces led by Kikkawa Motoharu marched toward Iwami Province to push back against the Amago clan of Izumo Province who were maneuvering to secure Iwami Silver Mountain that had been seized from the Ōuchi.  To prevent the Ōtomo clan of Kyūshū from interfering in their operations, the Mōri dispatched Kodera Mototake to Funai in the Ōtomo territory.  In the course of this diplomatic effort, the Mōri agreed to pacification by the Ōtomo of territory in Kyūshū that was controlled at the time by the Ōuchi.  In exchange, the Mōri requested that the Ōtomo not intervene in their operations in Suō and Nagato.  Furthermore, the Mōri aligned themselves with Ryūzōji Takanobu of Hizen Province in northwest Kyūshū just in case the Ōtomo turned into their enemies.

Invasion of the western portion of Suō Province

Assault on Susumanuma Castle

After a settling down of the occupation of the Kuga District and the redeployment of military assets, the Mōri forces who had moved their main base to the Yōkō Temple in Iwakuni aimed to attack Susumanuma Castle in the Tsuno District.  On 4/20 of 1556, a division of 5,000 soldiers led by Kobayakawa Takakage attacked but were repelled by Yamasaki Okimori (the lord of Numa Castle), Era Katanobu, and reinforcements from the Ōuchi army.  The castle defenders put a dam on the Kosuji River that ran near the castle which was surrounded on three sides by swamp lands, raising the water level to further strengthen their defenses.  There were said to be 3,000 soldiers in the castle, and as many as 10,000 including those who retreated in defeat from the Kuga District.  On 9/22, Mōri Takamoto led forces to attempt another attack, but remained stymied by the defenses.

In the second month of 1557, Mōri Motonari himself led over 10,000 soldiers to launch another attack against Numa Castle. Motonari established a base on the ridge that ran along Mount Midori behind Numa Castle to the north. Furthermore, Takamoto set-up a base on Mount Gongen to the east while Takakage made an encampment on Mount Hinokuma to the south.  Troops were also positioned at Kumano-o to the west of Mount Midori to defend against possible reinforcements from Yamaguchi.  Despite a valiant fight against attacks that commenced on 2/19, the defenders were overwhelmed in an all-out attack by the Mōri from early in the morning on 3/2 during which the troops laid bamboo rafts covered by mats to enable their approach across the swamp to the castle.   In the end, over 1,500 men and women (and, by some accounts over 3,000) in the castle were slaughtered.  This marked the first time that the Mōri forces utilized arquebuses in battle.  Owing to the fierce attack by the Mōri, Era Katanobu first surrendered, and then Yamasaki Okimori vacated Numa Castle.  Mōri Motonari desired that Okimori would serve on behalf of the Mōri clan, but Okimori firmly refused and killed himself.

In a folktale related to this battle at Numa Castle in the Susuma area, a lady traverses the swamp.  She is the newly wed wife of Yamasaki Takatsugu (Okimori’s son) who prior to the battle was forced to separate from her beloved husband.  Desiring to meet again, she sang to herself while crossing the swamp in a shallow area.  By observing her cross the swamp, the Mōri soldiers learned the location of the shallow area which they then utilized to attack the castle.

Internal collapse of the Ōuchi clan

As Motonari’s invasion of Suō proceeded, the retainers of the Ōuchi clan began to collapse from within.  Sue Nagafusa (the eldest son of Sue Harukata), along with his younger brother, Sue Sadaaki, holed up in the headquarters of the Sue clan at Tonda-Wakayama Castle, along with Toida Takamori, the deputy military governor of Iwami Province who fled from Itsukushima.  However, after the Tainei Temple Incident, Sugi Shigesuke, the orphan of Sugi Shigenori (the deputy military governor of Buzen Province killed by Harukata) attacked.  Shigesuke’s rebellion may have been coordinated with the Mōri, or the Mōri may have launched the attack itself.  Unable to maintain the defense, Nagafusa and others abandoned the castle, fled to the Ryūmon Temple, where he took his own life on 3/2.  (There is an alternative theory that Nagafusa was attacked by the Sugi army and died soon after the Battle of Itsukushima in the tenth month of 1555.)

Based on another theory, Nagafusa abandoned the stronghold of Tonda-Wakayama Castle, and holed up in the Ryūmon Temple, where the soldiers set about strengthening their defenses by constructing towers near the front gate and felled the bridge.  The Sue were then able to hold on for several months until attacked.

Shigesuke destroyed the Sue who were the enemy of his father, nevertheless, Naitō Takayo took issue with Shigesuke’s rebellion and planned to eliminate him.  Attempts by Ōuchi Yoshinaga to mediate failed, after which opposing armies clashed at Ushirogawara in Yamaguchi.  In this battle, the town of Yamaguchi burned and Shigesuke was struck down in Hōfu on 3/4.

After attacking the survivors of the Sue clan at Tonda-Wakayama Castle on 3/8, the Mōri army departed the castle on 3/12 to march on the Sanyō Road via the Ukino Ridge to Hōfu.  A division of the Ōuchi army led by Washizu Takamasa and Asakura Hirofusa totaling 2,000 troops was stationed at the Matsuzaki-Tenman Shrine on Mount Tenjin in Hōfu.  This division was decimated by a much larger Mōri army of as many as 20,000 men.  Outnumbered, the Washizu-Asakura forces were defeated by the Mōri near the Saba River while attempting a retreat to Yamaguchi.  Meanwhile, Migita Takakazu and Noda Nagafusa at Migitagatake Castle responded to Motonari’s counsel to surrender.  This surrender may have been in response to a letter from Motonari sent after he entered Tonda-Wakayama Castle, or in response to the approach of the Mōri army after their defeat of the Washizu-Asakura forces.  Minakata Narimasa became the chamberlain of Migitagatake Castle, while, after surrendering to the Mōri, Migita Takakazu served in the vanguard in an attack on Yamaguchi, achieving meritorious results including the toppling of a fortress on Mount Hikami.  After subjugating Hōfu, Motonari moved his main base to facilities that supported the Matsuzaki-Tenman Shrine from where he directed attacks on Yamaguchi.

The end of Ōuchi Yoshinaga

The Ōuchi were left only with the divisions led by Ōuchi Yoshinaga and Naitō Takayo.  After the Battle of Itsukushima, the remaining forces holed-up in the recently built yet unfinished Kōnomine Castle, while Shinji Takayoshi entered Himeyama Castle, an auxiliary castle to protect Kōnomine from the south.  However, during the battle between Sugi Shigesuke and Naitō Takayo on 3/4, the town of Yamaguchi was scorched, whereupon Yoshimi Masayori who sided with Masanori expelled 2,000 forces led by Nogami Fusatada of Watarigawa in the Abu District and approached Miyanoguchi.  Similar to the outcome in Kyōto, Yoshinaga and Takayo were not focused on defensive measures so they abandoned Yamaguchi and fled to Katsuyama Castle in the Toyoura District in Nagato.  Those at the main base of the Mōri learned of these developments on 3/15.

The Mōri army invaded Yamaguchi while the forces led by Shinji Takayoshi at Himeyama Castle surrendered.  The main division of the Mōri moved to occupy Yamaguchi, while Fukubara Sadatoshi was assigned a division of 5,000 soldiers to track down and kill Yoshinaga.  To block reinforcements from the Ōtomo clan (the home of his parent’s family), Motonari sent 1,000 mounted soldiers by road to Shimonoseki.  The Mōri dispatched the Murakami navy and Mōri navy led by Nomi Munekatsu to impose a naval blockade from the Suō Nada (the Suō open sea) to the Kanmon Straits and the entire shoreline of Buzen Province in northern Kyūshū.  In a letter from Motonari in late 1556, he praises Hotate Naomasa for an attack on the stronghold of Akamagaseki, whereby the path of retreat for Yoshinaga was quickly severed.  Motonari further recognized the achievements of Yoshimi Masayori who entered Yamaguchi in coordination with the Mōri army by hosting a celebratory banquet.

Yoshinaga was holed-up in the impregnable fortress known as Katsuyama Castle, defying attack by forces under Fukubara Sadatoshi who surrounded the castle.  Motonari then advised Sadatoshi that he would not pardon Takayo as a rebel and supporter of Sue Harukata, but Yoshinaga was only a puppet of the Sue toward whom Motonari held no enmity so he should be spared and sent back to the Ōtomo clan.  Sadatoshi received this advice in the form of a letter attached to an arrow.  Sadatoshi then convinced Yoshinaga while Takayo proceeded to take his own life on 4/2.  Yoshinaga vacated Katsuyama Castle and entered the Chōfuku monastery (later known as the Kōzan Temple) affiliated with the Sōtō school of Zen Buddhism.  Nevertheless, on 4/3, forces under Sadatoshi surrounded the temple, compelling Yoshinaga to kill himself.  Having been deceived, Yoshinaga had no options.  He took his own life after killing Nogami Fusatada, a loyal retainer who supported the Sue clan after the death of Sue Harukata, and the eldest son of Sue Nagafusa named Sue Tsurujumaru.  As a result, this ended the prospect of a legitimate heir for the Ōuchi and Sue clans, while Motonari’s conquest of Bōchō came to an end.  On 4/23, Motonari departed from Hōfu and returned triumphantly to Yoshida-Kōriyama Castle.

Uprisings by survivors of the Ōuchi clan

In the sixth month of 1557 (two months after the end of Motonari’s invasion of Suō and Nagato), Satō Sōsaemon-no-jō (father and son) used Motonari’s return to Aki as an opportunity to lead an uprising that was suppressed by Ichikawa Tsuneyoshi and Soshiki (Tomokane?) who had been assigned to defend Yamaguchi.  After the conflict, Motonari commended Nukushima Taneshige, a commander from the Ōuchi clan who had earlier surrendered, fought valiantly despite being injured.

Surviving senior retainers of the Ōuchi including the Sue, the Naitō, the Sugi, and the Toida summoned their allies and stirred uprisings across Suō and Nagato provinces.  On 11/10, other surviving retainers including the Kusaba, the Obara, and the Kawagoe backed Ōuchi Yoshitaka’s orphan, Toida Kikakumaru, and forced their way into Yamaguchi where they holed up at Shōjigadake Castle.  In response, on 11/11, Naitō Takaharu and Saika Takatoshi (allies of the Mōri staying in Yamaguchi at the time) took action to suppress these former retainers of the Ōuchi by launching a surprise attack against Shōjigadake and defeating remnants of the Ōuchi army in the Battle of Myōkensaki.  The Kusaba were killed in action while Kikakumaru was apprehended and sentenced to death.  In this battle, forces supporting the orphan of Sugi Shigesuke (Matsuchiyo, later known as Sugi Shigeyoshi) captured thirty-five heads of enemy soldiers.  Despite his injuries, Katsumata Morimichi killed two former retainers from the Toida clan, while Mitoshi Motosada and Arima Seizumi (世澄) made notable contributions.

Around the same time, other former retainers of the Ōuchi planned uprisings near Yamaguchi in Itoyone, but this was suppressed by Kuba Katanao after he detected the plans in advance through the collusion of a peasant named Yosaemon.  Former retainers also revolted in Nagato, but the high priest named Kata Morizane of the Sumiyoshi Shrine (a shrine of the first rank in Nagato) cooperated with Katsumata Narimori to suppress them.  Large-scale revolts by former retainers of the Ōuchi also broke out in the villages of Tokuji, Tonomi, and Tonda in Suō Province.  Hatano Katsuzane, a commander from the Ōuchi army who owned land in the Kiriyama township and had earlier surrendered to the Mōri, led forces to Migitagatake Castle in Hōfu to prevent uprisings in the Tokuji area.  Meanwhile, a servant of Kodama Naritada named Ōraku Hikosaburō positioned in Bessho Castle to block uprisings in the direction of Tonda and Tonomi.

After learning of the revolts, on 11/18, Motonari and Mōri Takamoto (his eldest son) deployed again, but by the time Motonari and his contingent arrived in Tonda around the end of the eleventh month, the disturbances had been almost entirely suppressed.  On 11/25, Motonari wrote a well-known letter to his three sons (Mōri Takamoto, Kikkawa Motoharu, and Kobayakawa Takakage) stating fourteen principles to live by while staying at the Shōei Temple in Tonda in Suō Province.  Motonari returned to Yoshida on 12/26.

Consequences for individual clans


By annexing Suō and Nagato provinces (the former territory of the Ōuchi clan), the Mōri at once significantly expanded their influence, becoming one of the most powerful daimyō families in the western region on a par with the Amago clan.  These developments gave rise to direct conflicts with the Amago in regard to control of the Iwami Silver Mountain and the Ōtomo of northern Kyūshū in regard to the commercial interests of Hakata.  Moreover, the Mōri did not completely eliminate resistance from the remnants of the Ōuchi clan until 1569.  During the subjugation of Suō and Nagato, Motonari had direct experience with the stiff resistance of locals.  To prevent looting and plundering by troops that were one of the causes of the resistance, Motonari prepared a written pledge with the name of twelve families from Aki Province.  This included the name of Kikkawa Motoharu who was not present for the march to Iwami during the Subjugation of Bōchō.  Meanwhile, there is no designated limit to the scope or time for the prohibitions, reflecting an aim to transform the Mōri clan from provincial lords to sengoku daimyō.


Owing to the death of Yoshinaga, the rule of the Ōuchi clan was extinguished, but Ōuchi Teruhiro (the younger cousin of Ōuchi Yoshitaka) survived.  In 1569, when battles persisted between the Mōri and Ōtomo clans in northern Kyūshū, Teruhiro forced his way into Yamaguchi with the support of the Ōtomo, but he then lost to the Mōri army and killed himself in an event known as the Revolt of Ōuchi Teruhiro.  As an outcome of this event, the Ōuchi clan disappeared from the stage of history.


Ōtomo Yoshishige of Bungo Province allowed his younger brother, Ōuchi Yoshinaga, to die without attempting to help, thereby reducing the influence of the clan in Suō Province.  However, the Ōtomo occupied their former territories of Buzen and Chikuzen provinces.  In the summer of 1559, the Ōtomo were appointed as the military governors of Buzen and Chikuzen provinces.  Although the Ōtomo maintained peaceful relations with the Mōri for a while, later, the clans clashed violently in northern Kyūshū over control of Hakata.  The Ōtomo helped devise the scheme for Ōuchi Teruhiro to invade Yamaguchi.


Through the offices of Masuda Fujikado, the Amago reconciled with the Ōuchi and entered into an allied relationship.  After a purge of their elite fighting force known as the shingūtō, the Amago strengthened their military as well as the authority of the main branch of the family, and then invaded Bizen Province to attack the Bizen-Uragami clan.  However, after the death in battle of Sue Harukata, the Ōuchi witnessed a decline in their influence over the Iwami Silver Mountain, providing an opportunity for the Amago to reclaim this site.  The Amago defeated an army led by Kikkawa Motoharu and Shishido Takaie upon their approach to Oshibara near the mountain in an event known as the Collapse at Oshibara.  The Mōri waited to recover the site until the execution of a peace accord with the Amago in 1562.


The Sue clan lost their lineage upon the death of the eldest son (Sue Nagafusa), but members of tributary families, Uno Motohiro and Sue Takamitsu, survived and became retainers of the Mōri.


Although Naitō Takayo killed himself, his uncle, Naitō Takaharu, survived to become the next leader of the Naitō clan and deputy militaery governor of Nagato Province.  The Naitō clan continued into the Edo period as members of the Chōshū domain.