Battle of Sekigahara

関ヶ原の戦い

西軍

Mino Province

東軍

Date:  9/15 of Keichō 5 (1600)

Location:  Sekigahara and the surrounding mountains in the Fuwa District of Mino Province (secondary battles defined by the conflict between the Eastern and Western armies occurred in regions across the country)

Outcome:  The Eastern Army led by Tokugawa Ieyasu prevailed over the Western Army led by multiple generals including, in particular, Ishida Mitsunari, Ukita Tadie, and Ōtani Yoshitsugu.  This battle had major consequences for the control of political authority, military power, territory, and wealth across the country.

Commanders:  Ishida Mitsunari, Ukita Hideie, Ōtani Yoshitsugu, Konishi Yukinaga, Shimazu Yoshihiro, Ankokuji Ekei

[Defense of Ōsaka Castle] Mōri Terumoto

[Ouu Division] Uesugi Kagekatsu, Honjō Shigenaga

[Ōtsu Castle Attack] Mōri Motoyasu, Tachibana Muneshige

[Defense of Mino and Owari] Oda Hidenobu

Forces:  Over 80,000

Losses:  8,000 to 32,600 (depending upon source)

Commanders:  Tokugawa Ieyasu, Kuroda Nagamasa, Asano Yukinaga, Ii Naomasa, Fukushima Masanori, Hosokawa Tadaoki

[Nakasen road] Tokugawa Hidetada, Sakakibara Yasumasa

[Forces to oppose the Uesugi and Satake]  Yūki Hideyasu

[Forces to defend Yamagata Castle] Mogami Yoshiaki

[Forces to defend Ōtsu Castle] Kyōgoku Takatsugu

Forces:  74,000 to 104,000

Losses:  4,000 to 10,000 (depending upon source)

Battle of Sekigahara

The Battle of Sekigahara occurred on 9/15 of Keichō 5 (1600) toward the end of the Azuchi-Momoyama period on fields known as Sekigahara in the Fuwa District of Mino Province.  The final showdown in Sekigahara was accompanied by battles across the country.  The Battle of Sekigahara may be understood to encompass these secondary battles as components of a broader conflict.  The site of the main battle is a nationally designated historical site.

Overview

This military conflict arose from political disputes within the Toyotomi administration after the death of Toyotomi Hideyoshi.  In addition to the main battle in Sekigahara, fighting broke out across the country between the Western Army led by Ishida Mitsunari and Ukita Hideie under Mōri Terumoto as the commander-in-chief in opposition to the Tokugawa and the Eastern Army led by Tokugawa Ieyasu.  As a result of this conflict, the Toyotomi administration lost their status as a unified political administration while, as the victor, Tokugawa Ieyasu, acquired momentous authority, creating a path for the establishment in 1603 of the Edo bakufu comprised of subservient domains under the rule of centralized authority led by Ieyasu as the supreme shōgun.

Prelude to the decisive battle

Conflicts within the Toyotomi family

Following the death of Hideyoshi in the eighth month of 1598, the Toyotomi administration transitioned from an autocratic model centered around Hideyoshi to a bureaucratic model whereby decisions were made by the Five Commissioners and Council of Five Elders who formerly served under Hideyoshi.  This was necessitated by the fact that Hideyoshi’s designated successor, Toyotomi Hideyori, was only five years old when he inherited the position.  Nevertheless, the absence of Hideyoshi gave way to political in-fighting so that the new structure gradually eroded from within and, as a result of the military conflict, was extinguished.

Potential reasons for the political disputes follow below, but the antagonistic relationship between the Eastern Army and the Western Army at the Battle of Sekigahara was marked by complexity, and, in the course of the conflict, there was a diverse range of motives for the actions taken by individual daimyō.  Moreover, fighting in the outer regions continued after the tenth month of 1600 despite the end of the decisive battle in Sekigahara and its political aspects.  These actions were not always directly connected to political differences among the central authorities.

Conflicts between the faction for centralization of authority and the faction for regional authority

Under one theory, the dispute had its origins in a conflict between two factions.  One faction, led by Ishida Mitsunari and Mashita Nagamori, sought to strengthen control of the Toyotomi administration (the central authorities) over the regional daimyō by taking steps such as the implementation of nationwide land surveys and associated policies to appropriate certain lands from the daimyō and to place those lands under the direct jurisdiction of the Toyotomi, in addition to active intervention in the internal affairs of those daimyō.  The other faction, led by Asano Nagamasa, aimed for appeasement of the regional daimyō and the decentralization of political authority.

Meanwhile, certain scholars question the basis of this theory of competing factions.  In 1593, Nagamasa transferred to Kai Province from where he provided support to assorted daimyō in the eastern region including the Date, the Nanbu, the Utsunomiya, the Narita, and others.  Thereafter, however, he strengthened control over copper mines owned by daimyō for the purpose of increasing the collection of transport levies, and reinforced the grip of the central authorities over marine transport in the Sea of Japan.  In addition, he advocated for removal of the Utsunomiya and Satake clans from their positions as daimyō, so it is not accurate to assert that he only aimed for appeasement and the decentralization of power.  Moreover, Nagamasa’s actions with respect to the eastern provinces served to highlight the concentration of power by the Toyotomi administration that produced a policy of all-out war requiring deployments to the Korean Peninsula.

Conflicts among retainers of the Toyotomi at the time of deployment to the Korean Peninsula

There is a theory that, with respect to the Keichō-Bunroku Campaign (the two expeditions to the Korean Peninsula), two conflicting factions emerged.  One faction was comprised of the hōkōshū, or the military organ of the administration led by Ishida Mitsunari and Mashita Nagamori, while the other faction, led by Katō Kiyomasa and Kuroda Nagamasa, was comprised of commanders of the forces in charge of crossing the seas.  These two factions came into conflict over issues of military strategy and the conferral of honors, serving as the primary reason for the Battle of Sekigahara.  This antagonistic relationship included a civil administrative faction primarily responsible for political affairs in the Toyotomi administration and a militaristic faction engaged in the conduct of military actions.

However, in terms of anecdotes indicating disharmony between these factions, many cannot be substantiated by primary sources or are believed to have been fabricated stories.  Meanwhile, there were confrontational relationships between bushō later affiliated with the Eastern Army.  Katō Kiyomasa and Tōdō Takatora disagreed in regard to the conferral of military honors for the Naval Battle of Shissenryō.  After the Battle of Ulsan Castle, Hachisuka Iemasa approved a proposal to reduce the battlefront which was proposed to Hideyoshi by the commanders in the field while Katō Kiyomasa took the opposite position.

Scholars note that the theory of a conflict between the civil administrative faction led by Ishida Mitsunari and the military faction led by Katō Kiyomasa originates from secondary sources in the form of military chronicles from the Edo period.  Thereafter, it became a stereotype in traditional research.  For example, Katō Kiyomasa, who received notoriety for military valor based on his image as one of the Seven Spears of Shizugatake, a group of elite warriors identified in later generations, did not, in fact make noteworthy contributions on the battlefield during that conflict.  From before the Bunroku-Keichō Campaign, he served as a representative of the Toyotomi administration with respect to the lands under their direct control as well as the governance of Higo Province following the removal of Sassa Narimasa from his position.

Discord between the Toyotomi family and retainers of the Toyotomi in regard to the Hidetsugu Incident

In the sixth month of 1595, Toyotomi Hidetsugu, the nephew and designated successor of Toyotomi Hideyoshi, committed seppuku in a dramatic event known as the Hidetsugu Incident.  There is theory that the antagonistic relationship between Ishida Mitsunari who led the purge of Hidetsugu and assorted daimyō influenced by this event served as a background for events leading to the Battle of Sekigahara.  Several of the daimyō to be punished for alleged complicity in a plot by Hidetsugu to rebel were given reduced sentences through the mediation of Tokugawa Ieyasu.  This forged a close relationship between these daimyō and Ieyasu as well as reinforced the resentment of these daimyō toward Mitsunari.

However, since the theory that Mitsunari was the ringleader of the incident was set forth in an account written in 1626, in subsequent military chronicles, the theory is based on anecdotal information that cannot be substantiated as historical fact.

Conflict between the magistrates of the Toyotomi administration and Tokugawa Ieyasu in regard to the last will of Toyotomi Hideyoshi

Prior to his death in the eighth month of 1598, Toyotomi Hideyoshi prepared a final will and testament along with a collection of laws and written pledges.  There is a theory that the hōkōshū, or magistrates, sought to conduct the affairs of the administration in accordance with these directives, while a faction comprised of Tokugawa Ieyasu and his supporters sought to deviate from these plans by seizing authority from within the administration, giving rise to conflict between the two factions.

After the death of Hideyoshi, Ieyasu took numerous steps in violation of the directives of Hideyoshi.  These included plans for political marriages between members of Ieyasu’s family and daimyō such as Date Masamune for personal reasons, the ouster of Hideyoshi’s formal wife (Kita-no-mandokoro, also known as Kōdai-in) and entry into the western citadel of Ōsaka Castle, individual decisions to increase the fiefs of daimyō that should have been approved by the clan elders and magistrates, allowing the wives and children of daimyō who had been hostages of the Toyotomi administration to return to their home provinces without permission.  Under this theory, these actions served as the basis for the effort of the Western Army to eliminate Tokugawa Ieyasu at the Battle of Sekigahara.

Meanwhile, soon after the death of Hideyoshi, on 8/27 of Keichō 3 (1598), four magistrates including Maeda Geni, Mashita Nagamori, Ishida Mitsunari, and Natsuka Masaie prepared, along with Mōri Terumoto, a written pledge expressing their loyalty to Toyotomi Hideyori and commitment to abide by the directives set forth by Hideyoshi.  These actions stood in contrast to those taken by Ieyasu in violation of the will of Hideyoshi.

Outbreak of political conflicts

Hideyoshi died on 8/18 of Keichō 3 (1598) in Fushimi Castle.  Conflicts within his political administration soon became manifest.  First, it was discovered that, immediately after Hideyoshi’s death, Tokugawa Ieyasu and assorted daimyō including Date Masamune planned political marriages for personal reasons in violation of the will of Hideyoshi.  Maeda Toshiie, a member of the Council of Five Elders, along with magistrates of the Toyotomi administration, took steps to investigate Ieyasu.  This nearly escalated to an armed clash between those supporting Toshiie and the backers of Ieyasu, but, following the exchange of written pledges, the situation appeared resolved.  According to one account written in the Edo period, during this event, almost thirty daimyō gathered in the residence of Ieyasu in Fushimi, including, among others, Oda Nagamasu, Kyōgoku Takatsugu, Date Masamune, Ikeda Terumasa, Fukushima Masanori, Hosokawa Yūsai, Hosokawa Tadaoki, Kuroda Yoshitaka, Kuroda Nagamasa, Tōdō Takatora, Katō Kiyomasa, Katō Yoshiakira, and Mogami Yoshiaki.

Meanwhile, those gathering in the residence of Toshiie included Mōri Terumoto, Uesugi Kagekatsu, Ukita Hideie, Hosokawa Tadaoki, Katō Kiyomasa, Katō Yoshiakira, Asano Nagamasa, Asano Yukinaga, Satake Yoshinobu, Tachibana Muneshige, Kobayakawa Hidekane, Konishi Yukinaga, Chōsokabe Morichika, Iwaki Sadataka, Hara Nagayori, Kumagai Naomori, Kakimi Kazunao, Fukuhara Nagataka, Oda Hidenobu, Oda Hidekatsu, Ishida Mitsunari, Natsuka Masaie, Maeda Geni, Nabeshima Naoshige, Arima Harunobu, and Matsura Shigenobu.

After Toshiie died in the third month of 1599, Ishida Mitsunari (one of the Five Commissioners) was attacked by Katō Kiyomasa, Fukushima Masanori, Kuroda Nagamasa, Tōdō Takatora, Hosokawa Tadaoki, Hachisuka Iemasa, and Asano Yukinaga.  Mitsunari, together with Satake Yoshinobu and Ukita Hideie (chief retainers) sought refuge in Mitsunari’s residence on the grounds of Fushimi Castle facing the western citadel.  The attack was triggered by their resentment based on the assertion that, in connection with the Siege of Ulsan toward the end of the Keichō Campaign on the Korean Peninsula, a relative of Mitsunari named Fukuhara Nagataka gave a falsified report to Hideyoshi resulting in the punishment after the war of Nagamasa and others for the conduct of improper acts.  However, Tadaoki and Masanori did not participate in the Siege of Ulsan and the punishment of Kiyomasa and Yukinaga cannot be confirmed from issued documents.

Based on a mediation by Ieyasu, Mōri Terumoto, Uesugi Kagekatsu, Satake Yoshinobu, and Kita-no-mandokoro (the formal wife of Hideyoshi), Mitsunari was removed from his position as a magistrate and confined to his base at Sawayama Castle.  The participation of Kita-no-mandokoro in the mediation (who was viewed as the most neutral party) substantiated the verdict as fair.  Meanwhile, Ieyasu may have earned a boost to his reputation.  However, as a means to resolve political differences, the launch of an armed attack by Kiyomasa and the others violated the directives of Hideyoshi.  Those involved in the attack were under the control of Ieyasu so the act was likely within the scope of actions permitted by Ieyasu.

Conquest of the Maeda clan of Kaga Province and the increasing authority of Tokugawa Ieyasu

On 9/7 of Keichō 4 (1599), Ieyasu departed from Fushimi Castle and entered Ōsaka Castle to meet Toyotomi Hideyori for the ostensible purpose of a giving a seasonal greeting to mark the blossoming of chrysanthemum flowers.  That same day, an assassination plot against Ieyasu was discovered.

The ringleader of the plot was Maeda Toshinaga, the eldest son of Maeda Toshiie and lord of Kanazawa Castle in Kaga Province.  Co-conspirators included Asano Nagamasa (one of the Five Commissioners), Ōno Harunaga (a close associate of Toyotomi Hideyori and Hideyori’s mother, Yododono) and Hijikata Katsuhisa (the lord of Nonoichi Castle in Kaga).  The plan was to enter Ōsaka Castle during Ieyasu’s visit and assassinate him.  According to one account from the early Edo period, Mashita Nagamori secretly informed Ieyasu of the plot. However, there are almost no primary sources of information concerning this incident so, with respect to the facts and its details, many points remain uncertain.

On 10/2 of Keichō 4 (1599), Ieyasu announced the punishments of those generals involved in the assassination plot.  Nagamasa was ordered to retire and be confined to Fuchū in Musashi Province, while Harunaga was exiled to Yūki in Shimōsa and Katsuhisa to Mito in Hitachi.  On 10/3, to eliminate the ringleader, Maeda Toshinaga, Ieyasu issued an order to assorted daimyō residing in Ōsaka for the Conquest of Kaga, instructing Niwa Nagashige, the lord of Komatsu Castle in Kaga, to leave the vanguard.  Upon hearing the news of the planned conquest, Toshinaga, from his base in Kanazawa, had to to decide whether to attempt to intercept the forces or to seek vindication.  Finally, he decided to send one of his senior retainers, Yokoyama Nagatomo, to meet with Ieyasu.  As proof of his integrity, Ieyasu demanded hostages.  The two sides reached a settlement whereby, in the first month of 1600, Toshinaga would send as hostages to Edo his mother, Hōshun-in (Toshiie’s formal wife), along with the children of senior retainers of the Maeda family including Maeda Nagatane, Yokoyama Nagakazu, Ōta Katsumune, and Yamazaki Nagatoku.  At this time, Toshinaga’s older sister was the wife of the eldest son of Hosokawa Tadaoki (Hosokawa Tadataka), raising Ieyasu’s suspicions that she was complicit in Toshinaga’s plot.  Similar to Toshinaga, he required her third son (Tadatoshi – fifteen years old) to come to Edo along with the other hostages as well as the third son of Asano Nagamasa (Nagashige – fifteen years old).

In the midst of this disturbance, Ieyasu entered the western citadel of Ōsaka Castle that was the former residence of Hideyoshi’s widow, Kita-no-mandokoro.  Thereafter, he continued to reside there.  Hideyoshi’s will stipulated that Ieyasu would reside in Fushimi Castle whereas residing in Ōsaka Castle violated those terms.  Having eliminated his political enemies and entered Ōsaka Castle which stood as the nucleus of political authority, Ieyasu achieved increasing power.  Governing from this base, he implemented increases to the fiefs of designated daimyō as well as transfers to new domains.  This appeared to have been for the purpose of increasing his allies so that he would have a majority faction.  He increased the fief of Hosokawa Tadaoki in Kitsuki in Bungo Province by 60,000 koku, the fief of Horio Yoshiharu in Fuchū in Echizen Province by 50,000 koku, the fief of Mori Tadamasa in Nagashima in Shinano Province by 137,000 koku, and the fief of Sō Yoshitoshi by 10,000 koku.  Owing to missteps during the Bunroku-Keichō Campaign, Fukuhara Nagataka incurred a reduction to his fief, while Tamaru Naomasa was transferred to Iwamura in Mino Province.  Originally, increases to the fiefs of daimyō or their transfers were decided on the basis of consultation and agreement among the elder magistrates of the administration, but Ieyasu proceeded on the basis of his own decisions.

In response to Ieyasu’s increasing authority within the administration, senior magistrates including Maeda Geni, Mashita Nagamori, and Natsuka Masaie cooperated with one another while Mōri Terumoto expressed his allegiance to them.  Meanwhile, Ishida Mitsunari, from his base in Sawayama, dispatched military forces to prepare for moves by the Maeda forces in the wake of the plot to assassinate Ieyasu.  He also offered his own residence in Ōsaka as a place to stay, demonstrating relatively friendly relations with Ieyasu.  However, these individuals made a final determination to engage in battle against Ieyasu.

Decision to subjugate the Uesugi clan in Aizu

In the midst of these political circumstances, from around the spring of 1600, the relationship between Ieyasu and Uesugi Kagekatsu deteriorated.  In the fourth month, a retainer of Ieyasu named Ina Akitsuna and others were sent to Aizu-Wakamatsu in Mutsu Province.  This party noted that the construction of Kōzashi Castle and a bridge over the Tsu River constituted acts of rebellion against the Toyotomi administration, engaged in an investigation, and demanded that Kagekatsu come to Kyōto early in the sixth month.  In the middle of the fifth month, Kagekatsu communicated his intention to visit the capital, but requested that the visit be postponed until the autumn and that those individuals who alleged that he was engaging in a rebellion by investigated themselves.  However, the demands from the Uesugi were not accepted and the visit to Kyōto early in the sixth month was canceled.  Moreover, in an inciteful letter to Ieyasu, Naoe Kanetsugu (the chief retainer of Kagekatsu) criticized the demand imposed upon Kagekatsu to visit the capital.  This is known as the Naoe Letter which still exists as a historical artifact, but questions remain with respect to its origin, its authenticity, and its interpretation.

Meanwhile, whereby negotiations with Aizu did not yield a conclusion by 5/3, Ieyasu had already decided to proceed with the Conquest of Aizu.  On 6/2, in the Oushū Notice, he directed Honda Yasushige and others to deploy toward the end of the seventh month.

According to one account, on 6/15, Ieyasu met with Toyotomi Hideyori and his mother, Yodo-dono, and received as farewell gifts 20,000 gold pieces, 20,000 koku of rice, a short sword from a renowned sword master (Masamune), and precious tea utensils (Narashiba).  Other accounts simply indicate that he received parting gifts without further detail.  On 6/16, Ieyasu departed Ōsaka and arrived at Fushimi Castle later that same day.  On 6/17, he is described as cheerful in spirit while seated in an inner tatami mat room.

Meanwhile, Uesugi Kagekatsu was coordinating with Satake Yoshinobu of Hitachi Province a plan for a pincer attack at the gateway to Shirokawa against the Tokugawa forces expected to invade the Uesugi territory.  However, certain scholars question whether earthworks built for a showdown in Shirokawa date to the year 1600 and there are inconsistencies between primary sources and the secondary sources that are the basis for the purported plans for a clash in Shirokawa, calling into question whether there was in fact such a plan.

Ieyasu’s eastward march with the aim of quelling the rebellion by the Uesugi provided an opening for Ishida Mitsunari to rise-up in the Kinai.  There is a theory that Mitsunari made a plan in advance with Naoe Kanetsugu (the chief retainer of Kagekatsu) to attack Ieyasu with forces from the east and west.  However, this theory appears in military chronicles and collections of anecdotes written in the Edo period, and is not directly supported by primary sources.  Based on a letter dated on 7/20 of Keichō 3 (1598) from Ishida Mitsunari to Sanada Masayuki, although this was written after the decision to raise the Western Army, there was no channel of communication established between the parties, so a coordinated plan did not likely exist.

Movements prior to the main battle

Eastward march by Tokugawa Ieyasu and entry into Ōsaka Castle by Mōri Terumoto

On 6/18, Ieyasu departed Fushimi Castle and, on 7/1, arrived in Edo.  On 7/7, he gave instructions to Mogami Yoshiaki, Akita Sanesue and other daimyō from the Tōhoku Region in regard to the invasion of Aizu and, informed them of plans to deploy on 7/21.  On 7/5, Ukita Hideie visited the Toyokuni Shrine in Kyōto to worship.  Those remaining in the vicinity of Kyōto, including Maeda Geni, Mashita Nagamori, and Natsuka Masaie (the “Three Magistrates”) on 7/12, sent a letter to Mōri Terumoto demanding that he come to Ōsaka while Mashita Nagamori sent a communication to Nagai Naokatsu (a retainer of Ieyasu) informing him that Ōtani Yoshitsugu was beset with an eye disease and of assorted matters concerning a deployment by Ishida Mitsunari.

In a letter dated 7/13, retainers of Mōri Terumoto including Shishido Mototsugu reported to Sakakibara Yasumasa, Honda Masanobu, and Nagai Naokatsu that, upon orders of Terumoto, Ankokuji Ekei was having the army that was marching east return from Ōmi to Ōsaka.  On 7/14, Kikkawa Hiroie sent the same report to Sakakibara Yasumasa.  In the letter, Shishido and the others questioned the involvement of Mitsunari and Yoshitsugu with respect to the return of the army to Ōsaka and noted that Terumoto did not show concern.

Upon orders to come to Ōsaka, on 7/15, Terumoto departed from Hiroshima and, on the same day, sent a letter to Katō Kiyomasa urging him to visit Kyōto as a sign of his loyalty to Hideyori.  Also on the same day, Shimazu Yoshihiro sent a letter to Uesugi Kagekatsu informing him that Mōri Terumoto, Ukita Hideie, the Three Magistrates, Konishi Yukinaga, Ōtani Yoshitsugu, and Ishida Mitsunari had raised arms on behalf of Hideyori and requested his consent to the action.

On 7/17, the Three Magistrates sent a communication 「内府ちがひの条々」to daimyō detailing the violations by Ieyasu following the death of Hideyoshi.  In addition, Terumoto and Hideie sent a letter to Maeda Toshinaga complaining of the breaches committed by Ieyasu.  That same day, Mōri Hidemoto entered the western citadel at Ōsaka Castle.  A retainer of Hosokawa Tadaoki named Ogasawara Hidekiyo refused a demand for hostages from the group of magistrates and, together with Tadaoki’s wife named Hosokawa Garasha (a Christian convert), took their lives at the residence of Tadaoki in Ōsaka.  According to a secondary source from the Edo period, Ishida Mitsunari was the main proponent of the demand for hostages.  However, in primary sources from this period, the “group of magistrates” refers to the Three Magistrates.  Moreover, the communication sent by the Three Magistrates contains a denunciation of Ieyasu for, on his own accord,  allowing the wives and children of assorted daimyō to return to their home provinces.  There is a possibility that Komatsu-hime, the wife of Sanada Nobuyuki and adopted daughter of Ieyasu had returned to her home province prior to the outbreak of hostilities.

On 7/18, Ishida MItsunari visited the Toyokuni Shrine in Kyōto to worship.  On 7/19, Mōri Terumoto entered Ōsaka Castle and the forces of the Western Army deployed in the direction of Tango Province.  Meanwhile, attacks by the Western Army commenced against Fushimi Castle defended by Torii Mototada (a retainer of Ieyasu).  On 7/22, forces under Ukita Hideie and, on 7/23, forces under Kobayakawa Hideaki, joined the attacking forces at the Battle of Fushimi Castle.  There is a theory that, initially, as a means of allying with Ieyasu, Shimazu Yoshihiro and Kobayakawa Hideaki expressed an intent to send forces to the aid of the defenders but were refused and therefore joined the Western Army instead.  However, this perspective is based on secondary sources written in the Edo period after the Battle of Sekigahara and cannot be authenticated.

Reversal by the daimyō of the Eastern Army

On 7/18, Inaba Michitaka returned to his home province owing to a postponement of the deployment in the Kantō.  However, on 7/19, Hidetada headed toward Aizu while Ieyasu deployed from Edo on 7/21.  As of this time, the Conquest of Aizu was not suspended.  According to letter dated 7/21 from Hosokawa Tadaoki to to his retainers including Matsui Yasuyuki, reports that Terumoto and Mitsunari had raised arms came one after another from Kyōto and its environs to those in Ieyasu’s territory.  On 7/23, Ieyasu informed Mogami Yoshiaki that an invasion of Aizu was not necessary owing to news that Mitsunari and Yoshitsugu were circulating notices to all the regions.  On 7/26, the assorted daimyō from Kinai and the western provinces who had assembled in the Kantō on behalf of the Eastern Army began a westward march.  Ieyasu also indicated an intention to soon go to Kyōto.  The military target of the Eastern Army at this time was Mitsunari’s base at Sawayama Castle.

On 7/27, Sakakibara Yasumasa sent a letter to Akita Sanesue informing him that Mitsunari and Yoshitsugu were set to rebel so Yodo-dono, the Three Magistrates, and Maeda Toshinaga demanded that Ieyasu come to Kyōto and that the command over operations in the direction of Aizu had transferred from Ieyasu to Hidetada.  However, on 7/29, the situation reversed in a letter from Ieyasu to Kuroda Nagamasa, Tanaka Yoshimasa, and Mogami Yoshiaki stating that the Three Magistrates were intent on rebelling.  At this time, the Kuroda and Tanaka forces were already headed west.  On 7/30, orders were given to Tōdō Takatora to march west.

On 7/25, in the village of Oyama in Shimotsuke Province, Ieyasu held a war council with assorted daimyō in the Eastern Army who were participating in the Conquest of Aizu.  In the Oyama Deliberation, the participants in the council decided to suspend the conquest and send their forces west.  However, there are no primary sources detailing the Oyama Deliberation so there are numerous theories concerning the existence, content, and meaning of this event.

Invasion of Ise Province by the Western Army and the attack on Gifu Castle

In a letter dated 7/26, the Three Magistrates inform Nakagawa Hidenari that 20,000 forces under Mōri Hidemoto were camped between Seta and Moriyama, and that if the Eastern Army marches west, there is a plan to intercept them, and, the forces under Ukita Hideie and Kobayakawa Hideaki were amassing in Daigo, Yamashina, and Ōtsu.  On 7/29, Ishida Mitsunari arrived in Fushimi.

On 8/1, Fushimi Castle was toppled.  That same day, Mōri Terumoto, Ukita Hideie and the Four Magistrates (the Three Magistrates plus Ishida Mitsunari) gave orders to Kinoshita Toshifusa to join Kinoshita Katsutoshi and go toward Kita-no-shō to prepare against Maeda Toshinaga who had advanced to Komatsh in Kaga Province.  On 8/3, Maeda Toshinaga attacked and toppled Daishōji Castle where Yamaguchi Munenaga of the Western Army was holed-up, whereupon Munenaga and hs son, Yamaguchi Nagahiro, took their own lives.

On 8/4, Ieyasu dispatched Ii Naomasa to daimyō including Fukushima Masanori and Ikeda Terumasa who were marching west so sent a letter to abide by his instructions.

On 8/5, returned from Komatsu to Edo, and, on the same day, Mitsunari returned to Sawayama.  Around this time, the Western Army was in the process of negotiating with Fukushima Masanori who was in Kiyosu Castle in Owari.  If this were to succeed, the Western Army would invade Mikawa, if not, then the Western Army planned to attack Kiyosu Castle.

On 8/8, a contingent of approximately 10,000 forces led by Kikkawa Hiroie and Ankokuji Ekei deployed, along with forces under Natsuka Masaie, to Ise Province.  Further, Ishida Mitsunari, after consultations with Oda Hidenobu (the lord of Gifu Castle), deployed in the direction of Owari Province.  At this time, Mōri Terumoto, with 30,000 troops under his command, planned to intercept Ieyasu at Hamamatsu.

On 8/17, Shimazu Yoshihiro arrived in Tarui in Mino Province, and, on 8/20, headed toward his home province of Satsuma in southern Kyūshū and made a request for reinforcements.

On 8/19, Kuroda Nagamasa notified II Naomasa and Honda Tadakatsu not to wait for Ieyasu to depart, to cross the Kiso River, and to march toward Inuyama Castle.

On 8/22, daimyō from the Eastern Army assembld in the environs of Kiyosu, and, that same day, a unit led by Ikeda Terumasa traversed the Kiso River and fought against forces under Oda Hidenobu and defeated them.  On 8/23, units under Fukushima Masanori attacked Hidenobu at Gifu Castle and forced his surrender, repelling Ishida and Shimazu reinforcements who rushed to the scene.

On 8/24, Tokugawa Hidetada departed from Utsunomiua to attack Ueda in Shinshū (Shinano Province).  Similar to Oda Hidenobu of Gifu Castle, Ishikawa Sadakiyo, the lord of Inuyama Castle was aligned with Western Army.  Also on 8/24, Ii Naomasa warned in a letter to Takenaka Shigekado (who was holed-up with Sadakiyo in Inuyama) to vacate the castle.

On 8/26, a contingent of 80,000 forces from the Eastern Army commenced a siege of Ōgaki Castle defended by a cavalry of 20,000 forces under the command of Hideie, Yukinaga, Mitsunari, Yoshihiro, and Hideyori.  Those in the castle requested reinforcements from the Mōri.

On 8/27, upon hearing of the fall of Gifu Castle, Ieyasu sent a letter praising the contributions of those daimyō who participated in the attack and instructed Fukushima Masanori to refrain from further military action until the arrival of Ieyasu himself and the forces led by Hidetada.  Meanwhile, after invading Ise and toppling Anōtsu and Matsuzaka castles, headed toward Owari.

Decisive battle and closure

On 9/1, Ieyasu departed from Edo.  In a letter dated that same day, he provided instructions agains to the commanders including Fukushi and Ikeda of the main force of the Eastern Army who around this time were gathered in Tarui to refrain from operations until Ieyasu himself arrived, and confirmed that Hori Naoyori intended to attack Ōgaki Castle by flooding.

On 9/2, Ōtani Yoshitsugu, Toda Shigemasa, Hiratsuka Tamehiro, Akaza Naoyasu, Ogawa Suketada, Kutsuki Mototsuna, and Wakisaka Yasuharu established a formation in the village of Yamanaka to the southwest of Sekigahara to secure the passage to the northern provinces.

On 9/3, Inuyama Castle was vacated.  On the same day, Hino Terusuke, Naka-no-in Michikatsu, and Tominokōji Hidenao departed as messengers headed to make a peace offer to Hosokawa Yūsai who was holed-up in Tanabe Castle in Tango Province.  From around this time, the Western Army began a siege of Ōtsu Castle following the earlier betrayal of its lord, Kyōgoku Takatsugu, to the Eastern Army.  However, with respect to the movements of Takatsugu, under one view, Takatsugu should be viewed as a member of the Eastern Army for two reasons.  First, his younger brother, Kyōgoku Takatomo, served as a member of the Eastern Army and was under Takatsugu’s influence; second, as of the seventh month, commanders in the Eastern Army recognized Takatsugu as one of their members.  Under another view, commanders in the Western Army were under the impression that he was on their side based on the fact that he was the younger brother-in-law of Yodo-dono and, for a while, acted as though he sided with the Western Army so it later appeared that he betrayed the Western Army in favor of the Eastern Army.

On 9/5, Sanada Masayuki, who at one time had offered to surrender to Tokugawa Hidetada, reversed his position and expressed an intent to resist.  He abandoned Toishi Castle and retreated to Ueda Castle.

On 9/7, Mōri Hidemoto and Kikkawa Hiroie arrived at Mount Nangu near Sekigahara in Mino Province.

On 9/9, Ieyasu advanced with his forces to Okazaki, on 9/10, to Atsuta, and, on 9/13, to Gifu.  On 9/14, the army arrived in Akasaka.  In one anecdotal account written in Kyōhō 12 (1727) of the Edo period, Shimazu Yoshirio proposed a nighttime attack on Ieyasu’s main position, but Shima Sakon opposed the plan while Ishida Mitsunari agreed with Sakon so the plan was not pursued.  However, there are no primary sources to substantiate a plan for a nighttime attack.

On 9/14, Kobayakawa Hideaki ousted Itō Morimasa and entered Matsuoyama Castle to the southwest of Sekigahara.  In the evening of 9/14, Ōtani Yoshitsugu arrived in Sekigahara.

On 9/12, Hosokawa Yūsai, who was holed-up in Tanabe Castle, received a direct Imperial order to wtihdraw from the castle.  Around 9/13, a settlement was reached between the Eastern and Western armies whereby Ōtsu Castle was vacated and, on 9/15, Mōri Motoyasu entered Ōtsu Castle.  That same day, the Eastern Army prevailed in a clash between the main divisions of the Eastern and Western armies at the Battle of Sekigahara.  On that same day, Ieyasu advanced with his forces to Sawayama.

On 9/17, Mōri Motoyasu retreated from Ōtsu Castle and, on the same day, Sawayama Castle was toppled.  Inside Ōgaki Castle, Akizuki Tanenaga joined his younger brother, Takahashi Mototane, and Sagara Yorifusa to kill Kumagai Naomori, Kakimi Kazunao, Kimura Yoshinobu, and his father, Kimura Toyotsune, whereupon they brought the heads of their victims and surrendered to the Eastern Army.  Thereafter, Fukuhara Nagataka, the commander in charge of defending the castle, continued to resist for over twenty days.  During this period, negotiations began between Mōri Terumoto and Ieyasu with Kuroda Nagamasa and Fukushima Masanori serving as intermediaries.  The parties settled on the basis that the rights to the Mōri’s then-current territories be recognized.  Nevertheless, in the tenth month, this agreement was scrapped when their territories were reduced to Suō and Nagato provinces.

On 9/25, Ieyasu and Hidetada confirmed that five individuals including Fukushima Masanori and Kuroda Nagamasa had entered Ōsaka Castle and Terumoto withdrew.

On 9/27, Ieyasu entered Ōsaka Castle and reconciled with Toyotomi Hideyori.

On 10/1, Ankokuji Ekei, Konishi Yukinaga, and Ishida Mitsunari were slayed at an execution site known as Rokujōgawara along the Kamo River in Kyōto.

Course of events on 9/15 of Keichō 5 (1600)

Almost all of the records concerning the formations and course of events on the day of the Battle of Sekigahara derive from compilations made after the battle by the bakufu and participating daimyō.  These constitute secondary sources in the form of military chronicles.  There are almost no records based on highly authenticated primary sources.  Despite covering the same battle, there are many inconsistencies in the contents of these secondary sources.

Records from primary sources

Two days after the battle, on 9/17, a letter was exchanged between daimyō who served as retainers of Tokugawa Ieyasu.  Specifically, Ishikawa Yasumichi and Hikozaka Motomasa jointly signed a letter addressed to Matsudaira Ienori that read as follows:

On 9/14, Ieyasu arrived in Akasaka and, around 10:00 AM on 9/15, he moved to Sekigahara where a battle occurred.  Forces led by Ishida Mitsunari, Shimazu Yoshihiro, Konishi Yukinaga, and Ukita Hideie burned down the outer enclosure of Ōgaki Castle and deployed to Sekigahara.

When forces of the Eastern Army led by vanguard units under Ina Naomasa and Fukushima Masanori continued attacks against the enemy position, Kobayakawa Hideaki, Wakisaka Yasuharu, and Ogawa Suketada (father and son) were cut from behind so the enemy forces fled in defeat.

Thereafter, pursuing forces killed Shimazu Toyohisa, Shima Sakon, Ōtani Yoshitsugu, Toda Katsunari, Hiratsuka Tamehiro, and others.

A letter dated 9/15 from Date Masamune to Tokugawa Ieyasu stated that the battle ended around Noon and, by the end of that day, Ieyasu arrived in Sawayama.

Records from secondary sources

With respect to the Battle of Sekigahara, there is a vast assortment of military chronicles, genealogies, memorandums and other secondary sources of information from which to gain an understanding the events that transpired on and around 9/15 of Keichō 5 (1600) in Sekigahara.  Although not authenticated, the following draws from among those sources that best describe the course of events.

Account from the Naifukō-gunki (Military Chronicle from the Ministry of Interior)

After Ieyasu arrived at Akasaka, battalions under Ishida Mitsunari, Konishi Yukinaga, Shimazu Yoshihiro, and Ukita Hideie pulled back into the mountains.  The next morning archery and infantry battalions totaling 20,000 soldiers led by Mōri Hidemoto, Kikkawa Hiroie, Chōsokabe Morichika, Ankokuji Ekei, and Natsuka Masaie conducted formations for vanguard units on Mount Okagahana to the south of Tarui.  Ieyasu sent Ikeda Terumasa and Asano Yukinaga in that direction while he led groups of hatamoto, or direct retainers, to establish a position between Nogami and Sekigahara.  On the morning of 9/15, rain and fog created conditions for poor visibility.  Around 10:00 AM, the sky cleared and visibility improved, whereupon patrol units from each side began to clash.  The Ishida, Konishi, Shimazu, and Nabeshima battalions traversed the Fuji River and headed southeast to the south of the village of Koseki and established a position.  Forces under Ōtani Yoshitsugu, Ukita Hideie, Hiratsuka Tamehiro, and Toda Katsushige located on Ishihara Ridge came down, crossed the Tani River, advanced to fields to the north of Sekigahara, and, with mountains behind them to the northwest, sent soldiers to the southeast.

In the Eastern Army, the vanguard units under Fukushima Masanori headed west on the Nakasen road (the main road to Sekigahara connecting Edo and Kyōto), units under Tōdō Takatora and Kyōgoku Takatomo advanced on the south side of this road, and, from the Hokkoku road (a secondary route for travelers going to the Zenkō Temple in Shinano Province), battalions led by Oda Yūrakisai, Furuta Shigenari, Inoko Kazutoki, Funakoshi Kagenao, and Sakuma Yasumasa participated in violent clashes.  Meanwhile, units under Kanamori Nagachika, Hosokawa Tadaoki, Kuroda Nagamasa, Katō Yoshiakira, Tanaka Yoshimasa led the charge from the front.  In the midst of the battle, Kobayakawa Hideaki, Wakizaka Yasuharu, Kutsuki Mototsuna, and Ogawa Suketada switched sides to the Eastern Army, whereupon the battalion led by Matsudaira Tadayoshi rushed forward.  Despite incurring several injuries, Tadayoshi contributed to the fight against enemy soldiers.  The forces under Ii Naomasa accompanied the Matsudaira in battle.  Naomasa fought valiantly with injuries.  Ōtani Yoshitsugu committed seppuku and Shima Sakon and his son (Shima Nobukatsu) along with Hiatsuka Tamehiro and Toda Katsushige died in battle.  The Western Army could not withstand a charge on the Nakasen road by forces under Honda Tadakatsu, and lost numerous soldiers in the subsequent pursuit while fleeing down along the Fuji River in the direction of Ibuki.  The forces of the Western Army on Mount Nangū also fled.  Ieyasu conducted an inspection of enemy heads taken, and, after allowing the soldiers a break, surrounded Sawayama Castle later that same day.

Account from the Sekigahara-shimatsuki (Outcome of Sekigahara)

With respect to formations of the Western Army, the Ishida battalion led by vanguard forces under Shima Sakon were based north of the village of Koseki along the mountains, and to their left along the mountains were forces led by Oda Nobutaka along with an elite cavalry unit call the Ōsaka giboroshū originally formed by Toyotomi Hideyoshi identifiable with yellow capes proudly worn while atop their horses.  The Shimazu were positioned behind the Ishida battalion.  To the south of the village of Koseki, in an area between the Hokkoku road and the Nakasen road were units from the Ukita, the Konishi, the Ōtani, the Hiratsuka, and the Toda.  To the south of the main road were units from the Kobayakawa, the Wakizaka, the Kutsuki, and the Ogawa.  To the rear of Mount Nangū were the Natsuka, the Ankokuji, the Kikkawa, and the Chōsokabe units.  The battle commenced around 8:00 AM.  Vanguard forces included the Fukushima, the Kyōgoku, the Tōdō, the Matsudaira, the Ii, and the Honda, along with the Tanaka, the Hosokawa, the Kuroda, the Katō, and the Kanamori in the second line, attacked the Ishida battalion.

Following attacks by Matsudaira and Ii forces, the Ukita and Shimazu soldiers fled in defeat and, while pursuing the enemy forces, Ii Naomasa was shot in the leg by a Shimazu soldier.  As the Honda battalion charged forward, battalions on Mount Matsu including the Kobayakawa switched sides to the Eastern Army, while the Ōtani battalion crumbled under the attack.  Ōtani Yoshitsugu committed seppuku while Hiratsuka Tamehiro and Toda Katsushige were killed in action.  Owing to the betrayal by other forces, the Ishida battalion fell into disarray and their troops scattered.  Losses among the Western Army exceeded 8,000 soldiers and the fighting subsided around Noon.  The battalions associated with the Western Army who were positioned in the direction of Mount Nangū did not engage in fighting whle the Kikkawa battalion did not move because Hiroie had colluded with Ieyasu.  On 9/16, the Eastern Army attacked the base of Ishida Mitsunari at Sawayama Castle.

Account from the Sekigahara-gunki-taisei (Complete Military Chronicle of Sekigahara)

With the Ishihara Ridge in the background, the Ukita battalion headed southeast to the front of the ridgeline.  From the side of the Western Army, the Toda and Hiratsuka forces were to the right.  Further to the right, in the foothills of Mount Matsuo, were the Ōtani, the Kutsuki, the Ogawa, the Wakizaka, and the Akaza battalions.  The Kobayakawa were on Mount Matsuo.  The Ishida battalion set-up their main encampment on Mount Koseki.  Vanguard units led by Shima Sakon, Maeno Tadayasu, and Gamō Yorisato stood-up fences in front of the village of Koike and established a position.  The Mōri, Shishido Mototsugu, the Chōsokabe, and Nabeshima Katsushige were on Mount Kurihara.  The Kikkawa, Fukubara Hirotoshi, the Natsuka, and the Ankokuji were on Mount Nangū.  To the left of the Ukita battalion were the Konishi, the Shimazu, and Oda Nobutaka.  The Fukushima battalion in the front lines headed toward the Ukita battalion.  The Ii and Matsudaira battalions pushed through the Fukushima battalion and clashed with the Shimazu forces.  Units led by the Hosokawa, the Kuroda, the Katō, the Tanaka, Ikoma Kazumasa, and Takenaka Shigekado charged the Ishida battalion.  Oda Yūrakusai and Oda Nagataka (father and son) and the Tōdō battalions headed toward the Ōtani battalion.  After commencing around 8:00 AM, a victor had not been determined by early afternoon.  After Kuroda Nagamasa persuaded the Kobayakawa to switch sides, Ieyasu questioned why their battalion did not move.  To gain insight, he headed toward their position and fired a shot from an arquebus to which there was no response.  However, once the Wakizaka (who were colluding with Tōdō Takatora), the Ogawa, the Kutsuki, and the Akaza battalions attacked the Ōtani units, then the Kobayakawa battalion joined.  Yoshitsugu committed seppuku, the Hiratsuka and Toda died in battle, and the Ukita battalion scattered.  The Ishida battalion then engaged the Oda and Tōdō forces who defeated the Ōtani, but, after holding on for a while, survivors from the Gamō fled in the direction of Mount Ibuki.

During the rout of the Western Army, and with escape routes severed, the Shimazu battalion attempted to breakthrough the enemy positions.  At this time, Shimazu Toyohisa was killed, but even with a force of only fifty troops remaining, managed to flee the battlefield.  Ii Naomasa was shot by the retreating Shimazu forces and fell from his horse.  Although Mōri Hidemoto attempted to respond to a request from Natsuka Masaie to deploy, Kikkawa Hiroie (in the vanguard of the Mōri forces) was colluding with Ieyasu and did not move so Hidemoto could not participate in the fighting.  Once the outcome had been determined, he left the battlefield and headed toward the Kansai region.  Approximately 32,600 soldiers of the Western Army were killed in action and the fighting ended around 2:00 PM.  In the evening of 9/15, the Natsuka, the Ankokuji, the Chōsokabe, and Nabeshima battalions began to come down the mountain without fighting.  By the following morning, the forces completed their withdrawal.  The Eastern Army then turned to attack the base of Ishida Mitsunari at Sawayama Castle.

As noted above, the primary theme that the fighting began in the morning hours and, after the betrayal by Kobayakawa and others, the Western Army collapsed, is commonly understood, but there are differences in the details beyond this broad picture.  Moreover, well-known rumors circulating on the day of the battle included conflicts between the vanguard forces of Fukushima Masanori and Ii Naomasa, the shooting by Ieyasu of an arquebus at the formation of Kobayakawa Hideaki, and a breakthrough by the Shimazu units of the enemy forces, but the details of these events differ based on the source material.

Regional implications

Ouu Region

False charges by Hori Hideharu is the traditional reason given for the expedition against the Uesugi, but this is called into question by letters indicating an intent by Hideharu to join the Western Army.  When Ieyasu decided to halt the Conquest of Aizu and to turn his forces west, Yūki Hideyasu gave orders those in the main division including Mogami Yoshiaki whose territory abutted the Uesugi and neighboring powers including Hori Hideharu and Date Masamune to keep a watch on Kagekatsu.  Yoshiaki, whose own territory had been severed on behalf of the Uesugi, could not avoid a clash with the Uesugi forces.  Yoshiaki combined with assorted generals from the Ouu Region in a bid to fight against the Uesugi, but, after receiving news of the outcome of Sekigahara, the generals left to stabilize their own provinces.  Aware that he had a numerical disadvantage, Yoshiaki proposed a settlement with the Uesugi on the condition that he terneder his eldest son (Mogami Yoshiyasu) as a hostage, but this did not culminate in a deal because the Uesugi learned of signs that Yoshiaki planned to join with Akita Sanesue of the Eastern Army to attack the Uesugi territory.  On 9/9, an army led by Naoe Kanetsugu came from the direction of Yonezawa Castle, but an army led by Shida Yoshihide from Shōnai made an incursionn into the Mogami territory.  Meanwhile, Onodera Yoshimichi attacked Yuzawa Castle in the Mogami territory.

When Date Masamune joined the Eastern Army on the dawn of Ieyasu’s victory, Masamune received a written promise from Ieyasu to increase Masamune’s territory by seven formerly held districts for a fief of 1,000,000 koku, known as the “1,000,000 koku Certificate.”  The Date forces attacked and occupied Shiroishi Castle in the Uesugi territory, and, on the condition this be returned, entered into a settlement with the Uesugi forces.

After the fall of Hataya Castle on 9/12, Mogami Yoshiaki dispatched his eldest son, Mogami Yoshiyasu, on 9/15 to request reinforcements from Date Masamune.  Within the Date family, Katakura Kagetsuna proposed that if the Date attack after having the Uesugi and Mogami fight one another, then the Date can remove the Uesugi forces and easily take control of Yamagata Castle.  Under one theory, Masamune was concerned for the welfare of his mother in Yamagata Castle.  Nevertheless, the decimation of the Mogami offered a means to address the threat posed by Uesugi Kagekatsu so, on 9/17, with Rusu Masakage serving as Masamune’s proxy in the role of commander-in-chief, reinforcements were sent on an offensive operation.  On 9/15, the main division under Naoe Kanetsugu began attacks against Hasedō Castle.  On 9/21, the Date reinforcements arrived at the Koshira River to the east of Yamagata Castle.  Kanetsugu fought bitterly against Sakenobe Hidetsuna and other Mogami forces.  He could not mount an attack against Hasedō Castle defended by Shimura Akiyasu and a small force so the situation evolved into a stalemate.  However, on 9/29, detailed reports in regard to Sekigahara came to each camp and the tide turned in favor of the Mogami.

Kanetsugu ordered a withdrawal, and, with himself serving in the rear guard, pulled back his forces.  The Mogami and Date armies launched a pursuit with Mogami Yoshiaki leading the charge to attack the retreating forces.  This turned into a melee, with Yoshiaki getting shot in the helmet among other incidents.  The forces led by Mogami Yoshiyasu caught-up and enabled the Mogami to escape from a precarious situation.  Kanetsugu’s forces returned on 10/4 to Yonezawa Castle, but the Uesugi forces left in the Mogami territory lost to the Mogami and individuals such as Shimo Hidehisa surrendered one after another.

Hokuriku Region

In an effort to support the attack against the Uesugi, on 7/26, Maeda Toshinaga led a contingent of 20,000 soldiers from his base at Kanazawa Castle in Kaga Province.  On 8/1, the army entered Kaga-Matsuyama Castle and laid siege to Daishōji Castle, defended by Yamaguchi Munenaga.  Munenaga responded by strengthening his defenses at Daishōji and sent messengers to Aoki Kazunori of Kita-no-shō Castle and Niwa Nagashige of Komatsu Castle to call for reinforcements, but these did not arrive on time.  On 8/2, Toshinaga sent Kuri Kurobei and Matsui Hisazaemon to Munenage to warn him to surrender, but Munenaga became upset and refused.  The Maeda forces then initiated attacks on the castle while Yamaguchi Nagahiro (Munenaga’s eldest son), had soldiers lay in wait near the castle for an offensive, but this plan failed owing to its early detection by Yamazaki Naganori of the Maeda forces.  The Yamaguchi then prepared for a siege of the castle.

Fighting escalated in the environs of the castle between the Maeda forces and the Yamazaki vanguard units with support from forces under Chō Tsuratsu trailing behind.  Nagahiro boldly went on the offensive, causing losses among the Maeda forces, but retreated to the castle after encountering a hail of arquebus fire by the Maeda infantry.  The Maeda forces surged forward while the Yamaguchi forces led by Munenaga and Nagahiro (father and son) counterattacked.  Nevertheless, with a total of around 500 soldiers, the Yamaguchi were greatly outnumbered by the 20,000 Maeda troops.  Finally, Munenaga announced his surrender from atop a fence.  After sustaining many losses, the Maeda forces refused his offer, and instead charged into the castle.  In the evening of 8/3, Daishōji Castle fell, whereupon Munenaga and Nagahiro took their own lives.  Munenaga called on Kizaki Chōzaemon, a retainer of Yamazaki Naganori, to take their heads.

Next, the Maeda surrounded Aoki Kazunori at Kita-no-shō Castle.  However, the Maeda were tricked by a rumor that Ōtani Yoshitsugu was leading a large army in support of the defenders, whereupon the Maeda quickly withdrew to Kanazawa.  Maeda Toshinaga split-off a portion of his troops, sending a detached unit toward Komatsu Castle defended by Niwa Nagashige.  On 8/9, Nagashige’s forces attacked the detached unit of the Maeda, and after defeating this unit, proceeded to attack the main division under Toshinaga, imposing losses in the Battle of Asainawate.  After reaching a stalemate, Nagashige settled and turned over Komatsu Castle.  Toshinaga returned to Kanazawa and re-ordered his forces.  On 9/12, Toshinaga departed Kanazawa but could not arrive at Sekigahara in time for the battle.  At this time, Toshinaga’s younger brother (Maeda Toshimasa), who was participating in attacks on Daishōji Castle, stayed in his base at Nanao Castle and did not join the Eastern Army.  Toshimasa had previously insisted on joining the Western Army so likely did not seek to move until the rescue of his wife and children who had been taken as hostages by the Western Army.  As a result, his landholdings were later siezed.

Shikoku

In Iyo Province, the Mōri army initiated an offensive against Katō Yoshiakira of Masaki Castle who sided with the Eastern Army.   Kōno Michiyori, the head of the Kōno clan that served as a former military governor of Iyo from the Heian period, was the adopted son of Kōno Michinao and the natural son of Shishido Motohide, a senior retainer of the Mōri clan, establishing a relationship between the Kōno and Mōri clans.  Michiyori, along with surviving retainers of the Kōno clan such as Hiraoka Naofusa and Sone Takafusa converged with retainers of the Mōri having connections with Iyo such as Murakami Takeyoshi and Murakami Motoyoshi (father and son) who crossed the Seto Inland Sea and landed in Mitsuhama to set-up an encampment.  This contingent of over 2,500 forces demanded that Masaki Castle be vacated, but an elder named Tsukuda Kazunari requested time to allow the women and children to seek refuge.  Together with others stationed in Iyo to protect the Katō territory, he launched a nighttime attack against the unsuspecting Mōri forces in an event known as the Nighttime Attack at Mitsuhama (or the Battle of Mitsu-kariyaguchi).  Motoyoshi died in the attack.  The defeat of the Western Army at Sekigahara placed the Mōri in a vulnerable position so the army withdrew while the Kōno, as allies of the Mōri, were unable to revive the clan.

In the case of the territory ruled by the Hachisuka clan in Awa and the territory of the Ikoma clan in Sanuki, the fathers of each of these clans sided with the Western Army while their sons joined the victorious Eastern Army.  Nevertheless, the fathers level of participation in the Western Army was insignificant, so their territories were occupied by the Mōri.  The Mōri clan had been steadily expanding their territory during the Sengoku period.  Around the time of the Battle of Sekigahara, the Mōri army attacked landowners across Shikoku in the name of the Toyotomi administration on the pretext of changes in the political situation.  Owing to the loss in a single day by the Western Army at Sekigahara, the Mōri ceased military operations and lost a lot of their landholdings on account of their prior actions opposed to the Tokugawa.

Awa Province

Among landowners in Awa, the Akamatsu clan abided by mobilization orders issued by Mōri Terumoto on behalf of the Toyotomi administration to join the Western Army.  Hachisuka Iemasa dispatched his eldest son, Hachisuka Yoshishige to the Eastern Army, but with only a small unit of eighteen mounted soldiers while many forces remained in Awa.  After Terumoto entered Ōsaka Castle and swept-out of the Toyotomi administration all of those who leaned in favor of the Tokugawa.  Iemasa, who was in Ōsaka at the time, was criticized for showing support for the Tokugawa and subjected to reduced circumstances, during which he underwent the rites of tonsure and underwent exile on Mount Kōya.  His band of retainers were folded into the umamawari, or cavalry, for the Toyotomi and sent to the northern provinces.  Morever, in a bid to control Ōsaka across the inland sea from Awa, orders were issued in the name of the Toyotomi administration.  Namely, until the outcome of Sekigahara was determined, Awa was placed under the temporary occupation of the Mōri.  On 7/29 when the Western Army was attacking Fushimi Castle, instructions were given in a document jointly signed by Mōri Terumoto (as the chief minister), along with Natsuka Masaie, Mashita Nagamori, and Maeda Geni (as magistrates) to retainers of the Mōri (Sanami Hirotada, and Murakami Motoyoshi and Murakami Kagechika (brothers)) to cooprate with retainers of the Hachisuka family to oversee Awa.  In the eighth month, in lieu of the Murakami brothers, other retainers of the Mōri including Mukunashi Kageyoshi, Niho Minbu-no-shōyū, and Miwa Motonori were sent to manage Awa.  On 9/19, after the outcome of Sekigahara was determined, Terumoto engaged in peace negotiations with Ieyasu whereupon he lifted the occupation of Awa, ordering the occupying forces to withdraw to Ōsaka and proposing the territory be returned to Hachisuka Iemasa.  On 9/25, the occupation army in Awa transferred Tokushima Castle to Masuda Hikoshirō of the Hachisuka family, bringing to an end the occupation of Awa by the Mōri army.

Sanuki Province

Similar to the situation in Awa, with respect to the Ikoma clan in Sanuki, Ikoma Chikamasa (a daimyō) sent his eldest son, Ikoma Kazumasa, to join the Eastern Army.  Kazumasa was recognized for his contributions during the Battle of Gifu Castle in a written commendation from Tokugawa Ieyasu.  While Chikamasa remained in Sanuki, he dispatched retainers to serve as his proxies on the side of the Western Army in the Siege of Tanabe Castle in Tango Province in the run-up to the Battle of Sekigahara.  The reason given for his support of the Western Army owed to the fact that he was in Ōsaka at the time that the Western Army raised arms so he had no choice other than to back them.  There is a theory that he planned so that, no matter which side prevailed, the Ikoma clan could survive.

In Sanuki, the Ikoma were similarly situated to the Hachisuka clan, under pressure from the Toyotomi administration which was in turn subject to the influence of the Mōri clan.  Chikamasa undertook the rites of tonsure and temporarily resided on Mount Kōya.  To the extent this occurred prior to the Battle of Sekigahara, it would not have been for the reason that he had supported the Western Army, although there is a theory that he his actions in support of the Eastern Army were subject to question.  Later, owing to the contributions by Kazumasa to the Eastern Army, the rights of the Ikoma family to their landholdings were recognized.  After a while, Ikoma Chikamasa returned to Sanuki and, in 1603, died in Takamatsu Castle.

Iyo and Tosa Provinces

Among landowners in Iyo, the Ogawa, the Ikeda, and the Kurushima clans abided by mobilization orders issued by Mōri Terumoto on behalf of the Toyotomi administration to join the Western Army.  While large-scale fighting did not occur in Awa and Sanuki provinces, in the direction of Iyo, upon the wishes of Mōri Terumoto, the Iyo invasion army engaged in scheming with respect to the territory of Katō Yoshiakira and Tōdō Takatora who sided with the Eastern Army.  These forces engaged in direct military operations in the territory of the Katō.  Shishido 景世 (who was in a position to inherit the former Kōno family) served as the commander-in-chief, while Katsura Mototsuna, Sone Kagefusa (a kokujin from Iyo), the Innoshima-Murakami clan along with, in the eighth month, Murakami Motoyoshi who was selected from the direction of Awa were dispatched to Iyo.

On 9/17, the Iyo invasion army that landed in Mitsuhama was subject to a surprise nighttime attack launched by a battalion of the Katō that remained behind to protect their territory under the command of Tsukuda Kazunari.  Murakami Motoyoshi and Sone Kagefusa were killed in this operation known as the Nighttime Attack at Mitsuhama.  The Mōri family responded to this defeat by dispatching Shinji Masayoshi and Kiya Genkō.  According to historical compilations of the Katō family, many members of the Katō army died fighting in Mitsuhama.  The remaining members of the Iyo invasion army left Mitsuhama and attacked inland, occupying the Nyorai Temple in Kume, acting in concert with Hiraoka Naofusa (a former retainer of the Kōno family who started an uprising at Ebara Castle) and the Masaoka clan.  On 9/19, a clash occurred at the Nyorai Temple.  The commanding officer of the Katō family named Kuroda Kyūbei Naotsugu was killed in action.  On 9/23, the fighting came to an end on Mount Mitsunoki, and, after receiving news of the outcome of the Battle of Sekigahara on the next day, the Iyo invasion army withdrew.

The Mōri clan did not directly invade the territory of Tōdō Takatora, but stirred uprisings by local retainers of the former Saionji clan (eliminated n 1587) such as the Hisaeda and the Yamada.  As a result, Mise Rokubei from the village of Matsuba in the Uwa District of Iyo colluded with the Mōri and started an uprising. Chikaraishi Harubei, the commander of ashigaru, or foot soldiers, of the army sent to suppress the uprising was killed in action.  After pulling back once to Itajima, through the efforts of a former retainer of the Utsunomiya clan named Kurita Kunai, the army was finally able to quell the uprising.

The Chōsokabe clan of Tosa abided by mobilization orders from Mōri Terumoto on behalf of the Toyotomi administration to serve for the Western Army.

Kyūshū

In Kyūshū, Kuroda Josui and Katō Kiyomasa primarily remained in their territories but battles occurred as they attacked the territories of daimyō associated with the Western Army.

Kuroda Josui

In the seventh month, after Ishida Mitsunari raised arms, Yoshitaka showed an intent to rebel against Ieyasu from Kyūshū.  Upon recognition of these events, on 9/9, Ieyasu departed Nakatsu Castle to deploy in Buzen and Bungo provinces.  The first objectives of Yoshitaka were Tomiku Castle held by Kakimi Kazunao and Aki Castle held by Kumagai Naomori in eastern Bungo.  Both lords were positioned at Ōgaki Castle in Mino while their retainers were defending the respective castles.  The attacks on both castles were temporarily suspended owing to the landing in Bungo of Ōtomo Yoshimune, responses to attacks on Kitsuki Castle, and the Battle of Ishigakibaru.  However, beginning on 9/17, the attacks recommenced and, on 9/24, the castles were vacated by the defenders and seized.  The main base of Mōri Takamasa at Hinokuma Castle and outlying base of Tsunomure Castle were also vacated and seized after 9/19.  In a letter sent by Kuroda Yoshitaka to Tōdō Takatora on 9/19 while the attacks were underway, he noted that he would like Ieyasu to facilitate so he could view the territory of the Western Army that Josui and Katō Kiyomasa carved-out on their own devices.

Nabeshima Naoshige of Saga Province had his son, Nabeshima Katsushige, join the Western Army.  Naoshige remained behind and, in the latter part of the ninth month, kept his territory after aligning with Kuroda Yoshitaka and Katō Kiyomasa.  In the absence of the lord of Najima Castle in the territory of Kobayakawa Hideaki, the Kuroda army advanced to Akizuki.  After negotiations, those left in charge of protecting the land agreed to attack Kurume, joined the Eastern Army, and were allowed to keep their territory.  Kurume Castle was in the territory of Mōri Hidekane.  With its lord absent, the Kuroda and Nabeshima armies attacked.  On 10/14, the castle fell to Yoshitaka.  Meanwhile, Nakagawa Hideshige was suspected of supporting the Western Army after the Munakata and Tahara clans formerly under his command abandoned him and joined in the Battle of Ishigakibaru.  Although he imposed losses upon the Kuroda army at the Battle of Saganoseki, around the tenth month, he proved his allegiance to the Eastern Army by toppling Usuki Castle in the territory of Ōta Kazuyoshi.  In the end, the castle was seized by Kuroda Yoshitaka.

Mōri Katsunobu

On 8/18, Mōri Katsunobu was sent as a messenger of Mōri Terumoto and the magistrates to the base of Katō Kiyomasa at Kumamoto Castle to convince him to join the Western Army.  Under one theory, while en route, Katsunobu received news that his army incurred significant damage during an attack on Fushimi Castle.  He then quickly returned to Kokura Castle so his retainers delivered the letter.  Retainers lost in the attack on Fushimi Castle, such as Mōri Kyūzaemon and Mōri Jinzaemon, were under the command of Mōri Katsunaga (Katsunobu’s son).

In the ensuing attack on Anōtsu Castle and at the Battle of Sekigahara, Katsunaga was placed under the command of Ankokuji Ekei along with Terumoto’s retainers, so he lost his own command, raising tensions within the family.  Kuroda Josui joined the Eastern Army and showed signs of preparing his forces for an attack.  The Mōri and Kuroda were in neighboring provinces across a strait.  Mōri Terumoto, the leader of the Western Army, dispatched retainers including Mizawa Tametora and Wada Shigenobu to Moji Castle in Katsunobu’s territory in Buzen Province and also placed Kokura Castle under the command of Terumoto’s forces to oppose the Kuroda.  However, owing to the subsequent defeat of the Western Army, Terumoto pulled back and Kokura Castle was taken over by the Kuroda.

In the conferral of awards after the Battle of Sekigahara, Kiyomasa became the lord of Higo Province with a fief of 520,000 koku.

Katō Kiyomasa

In the year prior to the Battle of Sekigahara, in 1599, a conflict arose between the Shimazu family and the Ijūin clan who served as senior retainers of the Shimazu known as the Shōnai Disturbance.  In the course of this conflict, Katō Kiyomasa was secretly supporting Ijūin Tadazane, the retainer who launched the rebellion.  This caused disfavor with Ieyasu who had been endeavoring to resolve the situation and, as a result, did not permit Kiyomasa to participate in the Conquest of Aizu.  With respect to the alienation between Kiyomasa and Ieyasu, As noted, Mōri Terumoto sent a letter via Mōri Katsunobu to Kiyomasa urging him to join the Western Army.  However, Kiyomasa received permission from Ieyasu to have Kiyomasa’s retainers and servants join the expedition to subdue the Uesugi so, in the event of an unexpected problem, he set the stage for communications with Ieyasu.

Immediately after the Oyama Deliberation, Ieyasu entrusted the retainers of Kiyomasa with a letter and had them return to their home province.  He instructed Kiyomasa to refrain from unilateral military actions until Ieyasu returned to Owari and recognized Kiyomasa’s participation in the Eastern Army.  These retainers returned home and are presumed to have given the letter to Kiyomasa in the latter half of the eighth month, but, during this time, Kiyomasa was communicating with Kuroda Josui and Matsui Yasuyuki (a senior retainer of Hosokawa Tadaoki and chamberlain of Kitsuki Castle) and promising his cooperation.  In Higo Province, Konishi Yukinaga of Uto Castle and Sagara Yorifusa of Hitoyoshi Castle were on deployment for the Western Army.  Based on a letter dated 8/12, Ieyasu permitted Kiyomasa at his option to carve-out Higo and Chikuzen.  This messenger, however, arrived in Kiyomasa’s territory on 9/10.

Kiyomasa marched from his base at Kumamoto Castle on 9/15.  Initially, he planned to rush to Kitsuki Castle in Bungo to aid the defenders against attacks from Ōtomo Yoshitsune,  but the Ōtomo army was decimated on this day at the Battle of Ishigakibaru.  Kiyomasa learned of the situation in a letter from Kuroda Josui, so, on 9/17, he gave-up the plan to go to Bungo and changed course toward the direction of the territory of Konishi Yukinaga.

Beginning on 9/19,  he attacked Uto Castle and, on 9/21, burned the area below the castle.  Konishi Yuikage, the chamberlain of Uto Castle (the home base of Yukinaga), along with Nanjō Mototaka and Naitō Joan, put-up stiff resistance, imposing losses on the Katō forces while requesting reinforcements from the Shimazu.  Shimazu Yoshihisa dispatched Shimazu Tadanaga and Niiro Tadamoto to Higo, holed-up in Minamata Castle, and attacked Ashikita in battles against the Katō army.  Owing to the loss by the Western Army at Sekigahara, on 10/20, Konishi Yukinaga took his own life while the Shimazu forces returned to Satsuma.  Moreover, on 10/17, a retainer of Kiyomasa named Yoshimura Sakon seized Yatsushiro Castle in the Konishi territory, while, from the eleventh month, the occupation and governance of Uto Castle by Kiyomasa began.

Tachibana Muneshige

Although originally associated with the Western Army, after receiving news that Gifu Castle had fallen, Kyōgoku Takatsugu joined the Eastern Army and holed-up in Ōtsu Castle. Tachibana Muneshige then combined with the Mōri forces to attack and force him to open the castle.  These operations prevented Muneshige from participating in the main Battle of Sekigahara.  Next, Muneshige traveled via Ōsaka and then by sea route to Kyūshū, arriving around the beginning of the tenth month at Yanagawa Castle in Chikugo Province.  Having sided with the Western Army, he was then attacked by the Kuroda, the Katō, and the Nabeshima.  On 10/20, he clashed with the Nabeshima forces on the northern side of the Yana River, losing senior retainers in battle including Tachibana Shigezane, Tachibana Munetsugu, and Nitta Shigezane, while a veteran named Ono Shigeyuki sustained serious injuries, marking a significant setback for Muneshige.  After receiving a letter with a seal from Ieyasu to recognize his property rights, on 10/25, he settled with Katō Kiyomasa.  Katō Masatsugu (a retainer of Kiyomasa) took over Yanagawa Castle.  Thereafter, Kiyomasa and Kuroda Yoshitaka formed an allied army in Kyūshū comprised of the Katō, the Kuroda, the Nabeshima, and the Tachibana, and prepared for an attack against the Shimazu clan.  Meanwhile, peace negotiations were held with Muneshige serving as an intermediary.  In the eleventh month, Ieyasu ordered a halt to attacks in Satsuma (the home province of the Shimazu), whereupon the plans to attack the Shimazu developed by Tokugawa Hidetada were shelved.  Although Shimazu Toyohisa of Sadowara died at the Battle of Sekigahara, his territory in Satsuma was protected.

Other commanders

Owing to illness, Itō Suketake stayed in Ōsaka, but, early on, had communicated with Ieyasu and the soldiers in his territory fought for the Eastern Army so his rights to his landholdings were recognized.  Two days after the Battle of Sekigahara, Sagara Yorifusa, Akizuki Tanenaga and his younger brother, Takahashi Mototane, colluded with the Eastern Army, killed several occupants, and took over Ōgaki Castle so continued in that capacity, but Miyazaki Castle (an outliying castle held by Mototane) was occupied by Itō Suketake.

Other locations

Kantō Region

Satake Yoshinobu, a daimyō from Hitachi Province, had close relations with Ishida Mitsunari.  Yoshinobu had secret plans to coordinate a pincer attack with Uesugi Kagekatsu against the Tokugawa army during their march for the Conquest of Aizu.  However, his father (Satake Yoshishige), his younger brother (Ashina Morishige who inherited the Ashina clan), and the chief retainer (Satake Yoshihisa) insisted he should join the Eastern Army and were vehmently opposed to Yoshinobu supporting the Western Army.  Despite being retired, given that, in a single generation, Yoshishige had turned the Satake clan into a major power in northern Kantō and the central portions of Mutsu Province, Yoshinobu could not disregard Yoshishige’s opinion.  Consequently, he was caught between his personal friendship with Mitsunari and the wishes of his father, so he ended up with an ambiguous position.  He dispatched bushō under his command to join Hidetada’s forces marching on the road between Edo and Kyōto.  Tagaya Shigetsune and small powers including Yamakawa Tomonobu, Sōma Yoshitane, and Iwaki Sadataka were in communication with Kagekatsu, but, in the background were the movements of Yūki Tomokatsu who had become a rōnin, or wandering samurai, after losing his position at the head of the Yūki family (members of the Utusnomiya clan) owing to the succession of the family by Yūki Hideyasu.

Ise Province

While en route to Sekigahara, the Mōri forces attacked targets in Ise such as Anōtsu Castle.  Tomita Nobutaka, the lord of Anōtsu Castle, surrendered and pledged to enter the priesthood while Furuta Shigekatsu of Matsusaka Castle engaged in settlement negotiations with the Mōri in a bid to buy time.  Ujiie Yukihiro and Ujiie Yukitsugu (brothers) at Kuwana Castle initially declared neutrality, but under pressure from the Western Army, joined their forces.  Thereafter, the Western Army attempted to attack Nagashima Castle defended by Fukushima Masayori (the younger brother of Fukushima Masanori), but, upon learning that the Eastern Army had gathered in Kiyosu Castle, changed course and headed toward Mino Province.

Iga Province

The Western Army that marched toward Anōtsu for an attack then proceeded to attack Ueno Castle in Iga with a force of 30,000 soldiers in an event known as the Siege of Ueno Castle.  Tsutsui Sadatsugu, the lord of Ueno Castle, had earlier deployed for the Conquest of Aizu and left the castle in care of his brother, Tsutsui Genba.  In anticipation of the attack, Genba vacated the castle without a fight and fled to Mount Kōya to seek penitence.  The castle was then occupied by Shinjō Naoyori.  Meanwhile, Tsutsui Sadatsugu, the lord of Ueno Castle who had deployed for the Conquest of Aizu, received a pardon from Ieyasu and returned to Iga Province.  Sadatsugu combined with local forces in Iga to attack his former base at Ueno Castle.  After the battle, Shinjō Naoyori and his son surrendered and withdrew.  Having recaptured Ueno Castle, Sadatsugu returned to Sekigahara and fought against Ishida Mitsunari.