The Battle of Ishigakibaru occurred on 9/13 of Keichō 5 (1600) at Ishigakibaru in the Hayami District of Bungo Province in northern Kyūshū.  The conflict was waged between Kuroda Yoshitaka (Josui) for the Eastern Army and Ōtomo Yoshimune for the Western Army.  This was one of numerous battles between local powers across the country occurring in the days leading up to the decisive Battle of Sekigahara on 9/15 of Keichō 5 (1600). 

Prelude

Following the demise of Toyotomi Hideyoshi on 8/18 of Keichō 3 (1598), within the Toyotomi administration, Tokugawa Ieyasu, a member of the Council of Five Elders, gained prominence.  Ieyasu was opposed by Ishida Mitsunari, one of the the Five Commissioners of the Toyotomi administration, triggering an intense power-struggle between the two factions.  In 1600, at the peak of this ongoing conflict, Ieyasu decided to launch the Conquest of Aizu based on the pretext that Uesugi Kagekatsu was building-up military capabilities in his territory.  Assorted daimyō who were patrons of the Toyotomi clan, such as Fukushima Masanori, Katō Yoshiakira, and Hosokawa Tadaoki participated in the Conquest of Aizu as a sign of their support for Ieyasu and opposition toward Mitsunari.  For similar reasons, Kuroda Nagamasa, who possessed a fief of 180,000 koku based at Nakatsu Castle in Buzen Province, led the Kuroda army to join the campaign.

This deployment led to a temporary waning of Ieyasu’s influence in Ōsaka and the Kinai area.  In the seventh month of 1600, Mitsunari took advantage of this opportunity to back Mōri Terumoto as the next leader and launch a rebellion.  In this way, the struggle originating from two factions in the Toyotomi administration widened into a final contest between those in the east and the west for control of the country, triggering conflict in many areas across Japan.

Kyūshū was no exception from the turbulence.  Kuroda Nagamasa led the main division of the Kuroda army to join the Conquest of Aizu, while his retired father, Kuroda Josui (Yoshitaka), remained behind to guard Nakatsu Castle.  A Christian daimyō, Josui performed key roles under Toyotomi Hideyoshi and, after the death of Hideyoshi, aligned with the faction supporting Tokugawa Ieyasu – the head of the Eastern Army.  Josui expended his funds to amass 3,600 rōnin, or wandering samurai, who combined with members of the castle garrison in addition to local peasants and merchants, forming an army of approximately 9,000 men.  On 9/9, this army began an invasion of neighboring Bungo Province in northern Kyūshū.  Bungo was the home province of the Ōtomo clan led by Yoshimune, a sengoku daimyō and the twenty-second head of the clan.

Landing by Ōtomo Yoshimune in Bungo Province

Owing to his missteps during the Bunroku Campaign on the Korean Peninsula, Ōtomo Yoshimune was removed from his position and taken into custody by Mōri Terumoto, but, later was sent to Satake Yoshishige.  Meanwhile, Yoshimune’s son, Ōtomo Yoshinori, was initially taken in by Katō Kiyomasa and then transferred to Tokugawa Ieyasu.  After residing in Edo, he served in the Conquest of Aizu as a member of the Eastern Army.  Many of those in the band of retainers were taken in by the Kuroda family of Nakatsu.  Tabaru Chikakata and Munakata Shigetsugu were elevated to serve as direct retainers of the Toyotomi family, becoming yoriki, or security officers, for Nakagawa Hidenari.  After turning himself over to Josui, Yoshihiro Muneyuki received a fief of 2,000 koku to serve under his relative, Tachibana Muneshige.  Following the death of Hideyoshi, Yoshimune and the others were pardoned and set free.

In the fourth month of 1600, through the consideration of Mashita Nagamori, Yoshimune kept a residence in Tenma in Ōsaka.  Ishida Mitsunari launched his rebellion in the seventh month, while, in the eighth month, Yoshimune was presented by Toyotomi Hideyori with funds, horses, and armaments, including 300 arquebuses.  He departed Ōsaka and headed toward his home province of Bungo.  Upon learning that Yoshimune was en route to Bungo, Josui dispatched a messenger and, in Kaminoseki in Suō Province, demanded that Yoshimune side with the Tokugawa.  At the same time, Yoshihiro Muneyuki, a former retainer serving the Tachibana family who was en route to merge with Ōtomo Yoshinori from Edo, met with Yoshimune and recommended that he side with the Tokugawa, but Yoshimune refused to do so and, with the support of Terumoto, Muneyuki accompanied Yoshimune to Bungo.

On the evening of 9/8, Yoshimune crossed the Seto Inland Sea, reaching the shore between Tomiku and Aki castles.  Prior to the break of dawn, he proceeded south on the Kitsuki Inlet and landed along the beach.  On the morning of 9/9, Yoshimune set-up a position in Tateishi and called for former retainers of the Ōtomo to gather, whereupon Tahara Chikakata and Munakata Shigetsugu (former retainers of the Ōtomo serving Nakagawa Hidenari) joined the forces.  To the east of Tateishi rose the sea, the Tsurumi mountains to the west, and the Asami River to the south.  These features made the location a natural stronghold.  Across the Sakai River to the north of Tateishi lay the fields and dense forests known as Ishigakibaru.

Attack on Kitsuki Castle

In 1599, Fukuhara Naotaka, the lord of Kitsuki Castle and the surrounding territory in Bungo Province was removed from his position.  On 2/27 of Keichō 5 (1600), the fief was granted as detached territory to Hosokawa Tadaoki, the lord of Miyazu Castle in Tango Province.  Tadaoki dispatched retainers, Matsui Yasuyuki and Ariyoshi Tatsuyuki, to govern the territory.  On 4/15, Tadaoki himself toured the territory and met with Kuroda Josui to discuss how to respond to expected conflicts in the near future.

On 8/26, after receiving news of the Conquest of Aizu, Tadaoki immediately headed east.  On 8/28, while preparations for war began at Kitsuki Castle after the receipt of information from Katō Kiyomasa of the landing by Ōtomo Yoshimune in Bungo, a messenger was urgently sent to Tadaoki.  Matsui Yasuyuki, a chief retainer of Tadaoki, remained at Kitsuki Castle and did not respond to repeated demands from Ōtani Yoshitsugu and the Toyotomi magistrates to join the Western Army so, on 8/4, Mōri Terumoto and Ukita Naoie sent a letter ordering him to vacate Kitsuki Clastle and dispatched Ōta Kazunari, the son of Ōta Kazuyoshi (the lord of Usuki Castle) as a messenger.  On 8/13, however, Yasuyuki, who was assigned to guard the castle, refused to comply.

On the evening of 9/10, Ōtomo forces departing from Tateishi to attack Kitsuki Castle were led by Yoshihiro Muneyuki as the commanding general, along with Kibe Gentatsu, Yoshihiro Shichizaemon, Shibata 統生 as the head of the infantry, and 100 rank-and-file soldiers.  Owing to collusion by Nohara Tarōemon from the outer citadel, fires were set below the castle and fighting broke-out from dawn.  On the side of Kitsuki Castle, Yasuyuki set-up an ambush on Mount Aihara to intercept approaching forces, killing Shibata 統生 en route to defeating the Ōtomo forces.  In this battle, the Akayu sub-temple at the Chōsen Temple, the Kannonzen Temple on Mount Entsū, and the Hōsen Temple on Mount Ōhira were burned down.

On 9/9, after receiving news that the Ōtomo had set-up a position at Tateishi, Josui dispatched the vanguard division to support Kitsuki Castle.  This included the first battalion of 1,000 men led by Kuno Jizaemon, Sogabe Goemon, Mori Yosobei, and Tokieda Shigetsugu and the second battalion of 1,000 men led by Inoue Kurōemon, Nomura Ichiemon, and Gotō Tarōsuke.  Josui himself deployed after them.  On 9/10, the vanguard division traversed the Akane Pass and, on 9/12, arrived at Kitsuki.  With following orders to wait for the main division under Josui, beginning in the morning of 9/13, the vanguard division merged with Kitsuki forces at Kannawa and proceeded toward Ishigakibaru.

On 9/9, the main division led by Josui departed Nakatsu Castle and, after passing through Usa-Takamori Castle (Kuroda Takatoshi) and Takada Castle (Takenaka Shigetoshi), on 9/10, traversed the Akane Pass, advancing to Kunisaki.  The forces the laid siege to Tomiku Castle (Kakimi Kazunao).  Shigetoshi, who at time had not made clear his position, assigned 200 soldiers to his son, Takenaka Shigeyoshi, to join the Kuroda army.

After the Ōtomo army attacked Kitsuki Castle, the Kuroda army deferred their plans to attack Kakimi Kazunao at Tomiku Castle and, during battle on 9/13, had retainers including Inoue Kurōbei and Tokieda Heidayū advance to Tōsei.  On 9/12, the main division of the Kuroda army attacked Aki Castle (Kumagai Naomori) and, on 9/13, defeated Naomori’s army after the forces charged out of the castle.  The Kuroda then headed toward Kitsuki Castle in support of the garrison.

Course of events

On 9/13, Kitsuki forces established a position on Mount Jissōji.  Around noon, the first battalion in the vanguard division of the Kuroda army clashed with Ōtomo forces who set-up a position in Ishigakibaru after passing through a road between Mount Jissōji and Mount Kakuden.  Kitsuki forces later joined the battle.  During this clash, Yoshihiro Muneyuki of the Ōtomo feigned defeat and pulled back to an area near the main base at Tateishi.  After the first battalion of the Kuroda pursued them, an ambush by Munakata Shigemune along with a counterattack led by Muneyuki resulted in the deaths of Kuno Jizaemon and Sogabe Goemon.

Next, the Ōtomo forces pursued the Kuroda forces fleeing in defeat to the environs of Jissōji.  The pursuers attacked the position of Matsui Yasuyuki, but, upon seeing there were many troops, instead aimed toward the encampment of the Kuroda army in the foothills and overwhelmed them.  On this occasion, Nomura Ichiemon and Inoue Kurōemon from the second battalion of the Kuroda army along with Kitsuki forces rushed to assist, defeating the Ōtomo while the hostilities drew down by the evening.

Prominent bushō from the Ōtomo forces such as Yoshihiro Muneyuki and Munakata Shigemune were killed.  After arriving at Jissōji on 9/14, Josui conducted an inspection of heads of enemy soldiers and held a war council.  That same day, after learning of the defeat, Yoshimune attempted to take his own life but was admonished by Tahara Chikakata and, instead, underwent the rites of tonsure and appeared as a priest.  He dispatched Chikakata to meet Mori Tomonobu at the encampment of the Kuroda army and surrendered to Josui, bringing an end to the Battle of Ishigakibaru.  In support of Josui and Matsui Yasuyuki, Katō Kiyomasa of Higo Province came to Uchinomaki on 9/14 and to Oguni in the Aso District on 9/15, but, after receiving news of Yasuyuki’s victory, returned to Kumamoto.

Aftermath

After surrendering, Yoshimune was taken from Nakatsu to the custody of Kuroda Nagamasa in Ōsaka.  Owing to pleas from Yoshitaka and others, he was incarcerated in Shishido in Hitachi Province, later dying in 1605.  Tahara Jōnin apologized for absconding from the Nakagawa family to join the Ōtomo, and returned to service.  However, as a condition of his return, he participated in an assault against Ōta Kazuyoshi at Usuki Castle and was killed in action in Saganoseki.

One day after defeating the Ōtomo army, from 9/16, Kuroda Josui recommenced the offensive, and, from 9/17, laid siege to Aki Castle defended by a retainer of the Kumagai named Kumagai Geki, capturing the site on 9/19.  Most of the castle garrison then came under his command.  From 9/23, he assaulted Tomiku Castle defended by Kakei Riemon, a retainer of the Kakimi family.  On 10/2 his forces garnered control of Tomiku Castle, after which he freed the defenders and allowed them to join his army.  From 10/4, he marched north, and, on 10/5, he attacked Kawaradake Castle defended by Mōri Sadafusa, a retainer of Mōri Yoshinari, also capturing Kokura Castle.  During this time, in the course of pacifying Bungo Province, the Kuroda army acquired defeated soldiers and expanded their territory, swelling to a force of 13,000 men.  On 9/15, the day of reckoning at Ishigakibaru, the Eastern Army led by Tokugawa Ieyasu defeated the Western Army led by Ishida Mitsunari at the Battle of Sekigahara in Mino Province so the military operations conducted by Josui were halted upon orders of Ieyasu.

Kuroda Josui led mercenaries in battle against the Ōtomo army.  Possible reasons given for toppling castles of the Western Army include a desire to expand his territory or the ambition to pacify all of Kyūshū and compete against Tokugawa Ieyasu to become the supreme leader of the country, but the facts remain uncertain.  Nevertheless, Josui’s battles in Kyūshū such as to pacify Bungo Province resulted in victories for the Eastern Army which had few allies.  Furthermore, at the main Battle of Sekigahara, the contributions of Kuroda Nagamasa were recognized so the Kuroda clan received from Ieyasu a fief of 523,000 koku in Fukuoka in Chikuzen Province.

Yoshimune’s life was spared, but he was not permitted to revitalize his family.  His eldest son and heir, Ōtomo Yoshinori, became an attendant of Tokugawa Hidetada and the family named was preserved.

Battle of Saganoseki

After Tahara Chikakata and Munakata Shigetsugu fled their positions as guest security officers of Nakagawa Kiyoshige to join the Ōtomo forces, they stole the Nakagawa family banner and joined in the Battle of Ishigakibaru.  Having observed these developments, Josui notified Ieyasu that Hidenari had aligned with the opposing Western Army.  Hidenari sought to explain himself, but was not absolved of suspicion, and ordered Kiyomasa to track and kill Chikakata and Shigetsugu.  To grasp the situation, Kiyomasa prioritized an attack against Uto Castle of Konishi Yukinaga, and, in a bid to vindicate himself, Hidenari sent a hostage.  To further clarify his position, Hidenari commenced an attack against Usuki Castle with the aim of eliminating Ōta Kazuyoshi of the Western Army.  Having been defeated at the Battle of Ishigakibaru, Chikakata relied upon Shibayama Shigenari (the naval magistrate for the Nakagawa family) and fled for safety to Imazuru.  Hidenari also ordered Shigenari to attack Usuki Castle so Chikakata accompanied him as a member of the Nakagawa forces, converging with forces led by Nakagawa Nagasuke – the chief retainer.

On 10/3, the two armies violently clashed at Saganoseki.  The Nakagawa lost over 230 men, including Nakagawa Heiemon (the chief retainer), Tahara Chikakata, and Shibayama Shigesuke (the adoptive father of Shigenari), in addition to over 200 wounded.

Upon learning of the defeat of the Western Army at the Battle of Sekigahara, Ōta Kazuyoshi abandoned Usuki Castle and fled for safety.  In this manner, the Nakagawa family incurred many casualties,  but earned the trust of Ieyasu and were permitted to continue as daimyō.