# Battle of Sekigahara

The Battle of Sekigahara (Shinjitai: 関ヶ原の戦い; Kyūjitai: 關ヶ原の戰い, Hepburn romanization: Sekigahara no Tatakai), was an important battle in Japan which occurred on October 21, 1600 (Keichō 5, 15th day of the 9th month) in what is now Gifu Prefecture, Japan, at the end of the Sengoku period.
This battle was fought by the forces of Tokugawa Ieyasu against a coalition loyal to the Toyotomi clan, led by Ishida Mitsunari on behalf of the young child Toyotomi Hideyori, from which several commanders defected before or during the battle, leading to a Tokugawa victory. The Battle of Sekigahara was the largest battle of Japanese feudal history and is often regarded as the most important.
Mitsunari's defeat in the battle of Sekigahara is generally considered to be the beginning point of the Tokugawa shogunate, which ruled Japan for another two and a half centuries until 1868.

## Background

The final years of Toyotomi Hideyoshi's reign were turbulent. At the time of Hideyoshi's death, his heir, Toyotomi Hideyori, was only 5 years old, causing a power vacuum in Japan.

### Feuding factions

In the years following the Imjin War and the death of Hideyoshi, factional disputes arose between Ishida Mitsunari and seven former Toyotomi generals including Katō Kiyomasa. After the subsequent death of Maeda Toshiie, a powerful and long-term ally of Hideyoshi and Oda Nobunaga, who had been sympathetic to Mitsunari’s posturing, the uneasy balance of power began to dissolve. Tokugawa Ieyasu gathered both Kiyomasa and Fukushima Masanori to his cause in a bid to challenge the opposition from Mitsunari, who claimed to fight on behalf of the Toyotomi clan.
At this time, political tensions were high in the capital; rumors circulated of assassination attempts towards Ieyasu, while Toshiie’s son, Maeda Toshinaga, was accused of being involved in such conspiracies and contentiously but peacefully made to marry into the Tokugawa clan. Uesugi Kagekatsu, one of Hideyoshi's regents, stood against Ieyasu by building up his army, which Ieyasu officially questioned, demanding answers from Kyoto about Kagekatsu's suspicious activity. Naoe Kanetsugu responded with a mocking letter highlighting Ieyasu's own violations of Hideyoshi's orders.
Mitsunari met with Ōtani Yoshitsugu, Mashita Nagamori and Ankokuji Ekei, conspiring to raise an anti-Tokugawa army, of which Mōri Terumoto was appointed to be the overall commander. This coalition formed what came to be referred to as the Western Army. Terumoto immediately marched and captured Osaka Castle while the main army of the Tokugawa were still on their way to suppress Kagekatsu.
At first, Mitsunari wanted to use Gifu Castle, which at that time was commanded by Oda Hidenobu (the grandson of Nobunaga), and Ōgaki Castle as choke points to impede the advances of the Eastern Army (the Tokugawa-led coalition). However, this plan was foiled by a number of campaign events:
* Gifu Castle was captured by the Eastern Army under Fukushima Masanori and Ii Naomasa before the main forces of the Western Army arrived.
* On October 19, Shimazu Yoshihiro's troops were beaten by Mizuno Katsunari in a battle outside Sone Castle, after which Katsunari razed the outer moat of Ōgaki Castle and forced Yoshihiro to retreat into Ise Province.
* Mitsunari realized that the Tokugawa army was heading towards Osaka Castle.
Following these failures and the threat against Osaka Castle, Mitsunari changed his plan and prepared his army for an open battle on the field of Sekigahara against the main body of the Eastern Army, led by Ieyasu. As preparation for this inevitable conflict, Ieyasu had purchased massive quantities of Tanegashima matchlocks.
However, one day before the beginning of the battle, Kikkawa Hiroie, vassal of the Western Army-allied Mōri clan, colluded with the Eastern Army and promised that the Mōri clan would change sides during the battle, on the condition they would be pardoned after the war. Kuroda Yoshitaka and Kuroda Nagamasa served as representatives of the Eastern Army in this correspondence with Hiroie. Hiroie and his senior retainer Fukubara Hirotoshi presented hostages to the Tokugawa side as proof for their cooperation with the latter.

## The battle

At dawn on October 21, 1600, the Tokugawa advance guard stumbled into Ishida's army; neither side saw each other because of dense fog caused by earlier rains. Both sides panicked and withdrew, but each was now aware of their adversary's presence and location. Mitsunari placed his position in defensive formation, while Ieyasu deployed his forces south of the Western Army position. Last-minute orders were issued and the battle began. Traditional opinion has stated the battle began around 8:00 am; however, recent Japanese historians' research estimates that the battle actually began closer to 10:00 am.
The battle started when Ii Naomasa, previously heavily involved in the Battle of Gifu Castle, commanded his famed unit of 3,600 crimson-clad Ii no Akazoane ("Ii's red devils") to attack the center of the Western Army. According to historian Watanabe Daimon, by many indications of the battle records, the assignment of Naomasa as ichiban-yari (the first unit to engage the enemy) suggests the armies may have already been settled before the battle. Fukushima Masanori concurred with Naomasa's intention to lead the first attack, as Naomasa was appointed by Ieyasu as the supreme field commander and was therefore responsible for all commands and strategies during the battle.
Naomasa charged forward with 30 spearmen and clashed with the ranks of the Western Army. Meanwhile, Fukushima Masanori advanced from his position, following Naomasa and immediately engaging with troops led by Ukita Hideie.
At this point, the battle entered a deadlock. Ōta Gyūichi, who was present at the battle, wrote in his chronicle that "friends and foes are pushing each other" and "gunfire thunders while hails of arrows fly in the sky". According to records from Spanish accounts, 19 cannons from the De Liefde [nl], a Dutch trading ship, were also used by the Tokugawa army in this battle.

### Western Army defectors

During the battle of Sekigahara, several commanders of the Western Army changed sides, allying with the Tokugawa and changing the course of the battle. Perhaps the most notable of these defectors was Kobayakawa Hideaki, the nephew of Toyotomi Hideyoshi, whose disgruntlement with his uncle was exploited by the Tokugawa to sway his loyalty. Two prevailing theories exist regarding the timeline of Hideaki's defection:
* The conventional theory regarding Hideaki's defection suggests that the defection occurred partway through the battle. Although he had agreed to defect to the Tokugawa side beforehand, Hideaki was allegedly hesitant during the battle and remained neutral, reportedly only joining the battle around noon as a member of the Eastern Army. Some later historical accounts claim that as the battle grew more intense, Ieyasu finally ordered his arquebuses to fire at Kobayakawa's position on Mt. Matsuo to force a choice. This version allegedly originated from an anecdote about Hideaki dating to the Edo period.
* Modern Japanese researchers of Sekigahara, such as Jun Shiramine and Junji Mitsunari, have advanced the theory that Hideaki had already defected to the side of Tokugawa by the start of the battle, based on correspondence documents between Hideaki and Kuroda Nagamasa before the battle, as well as Ōtani Yoshitsugu's army position at the start of the battle suggesting foreknowledge by the Western Army of Hideaki's betrayal. Historian Stephen Turnbull also argues that the sheer distance between the Eastern Army positions and that of Kobayakawa, far out of range of arquebuses and likely too far for a shot to even be heard, makes the "story about Ieyasu ordering ‘cannon-shot’ into his ranks" to force Hideaki's hand very unlikely. Furthermore, Yūichi Goza explains that the story of Ieyasu shooting at Hideaki's location comes from secondary sources from the Edo period, suggesting it may have been the result of dramatization and embellishment from pro-Tokugawa shogunate historiography to aggrandize Ieyasu's success in Sekigahara.
Regardless of what actually transpired, the turncoat Kobayakawa forces overwhelmed Yoshitsugu's position. At the same time, Yoshitsugu's troops also engaged the units led by Tōdō Takatora, and Oda Yūraku.
Following the defection of Hideaki, Western Army leaders Wakisaka Yasuharu, Ogawa Suketada, Akaza Naoyasu and Kutsuki Mototsuna also changed sides, further turning the battle in the Eastern Army's favor. These four commanders are recorded to have established contact and concluded deals with Tōdō Takatora, one of the main commanders of the Eastern Army, several days before the battle.
Mōri Terumoto, then daimyō of the Mōri clan, also defected from the Western Army during the battle by keeping his forces entrenched at Osaka Castle rather than joining the battle, then sending his vassal Kikkawa Hiroie to quietly surrender to Ieyasu afterward. Professor Yoshiji Yamasaki of Toho University states that any neutrality-for-territorial-preservation agreement was ineffective at best and badly backfired for the Mōri at worst, as their domains were greatly reduced by the Tokugawa following the battle, and some Mōri troops notably did fight with the Western Army at Sekigahara rather than maintaining their neutrality. Sentiments of defection were divided among the Mōri; Mōri Hidemoto, cousin of and commander under Terumoto, genuinely attempted to meet and aid the Western Army, though his efforts were sabotaged by Hiroie, who, under the pretense of being busy eating his meal, stationed his troops in front of Hidemoto, obstructing them from advancing and relieving Mitsunari. Hiroie also obstructed another Western Army contingent led by daimyō Chōsokabe Morichika from marching and attacking the Tokugawa forces.

### Collapse of the Western Army

One of the first and most notable weak points within the Western Army forces developed on Ukita Hideie's front. During the engagement, Hideie's forces began to wane and were steadily overcome by the forces of Fukushima Masanori due to the latter's superior troop quality. The disparity in combat effectiveness may have been attributable to the prior insurrection within the Ukita clan, which caused many senior samurai vassals of the Ukita to desert and join the Tokugawa faction. Hideie was thereby forced to enter Sekigahara with fresh recruits of rōnin mercenaries to fill the gap left within his army. This proved fatal over the course of long-term combat against the Fukushima clan's more disciplined and trained regular troops; the Ukita clan ranks began to break and finally collapse under pressure despite outnumbering the Fukushima.
To the south, Ōtani Yoshitsugu was outnumbered in a successful attack led by Kobayakawa Hideaki; Yoshitsugu committed suicide and his troops retreated shortly thereafter. The Ōtani retreat left the Western Army's right flank wide open, which Masanori and Hideaki then exploited to roll the flank of the Western Army. Mitsunari, realizing the situation was desperate, also began retreating his troops. Meanwhile, Western Army commander Shima Sakon was engaged by the troops of Kuroda Nagamasa, who had taken a detour on the north to flank the Mitsunari and Sakon positions. In the end, Sakon was shot and fatally wounded by a round from an arquebus.
Following the capitulation of Sakon's unit, Shimazu Yoshihiro found his troops completely surrounded by Masanori and Honda Tadakatsu from the front, while Hideaki troops attacked his rear. The Shimazu troops only managed to break their encirclement after devastating casualties, escaping with only 200 soldiers remaining; even then, they were pursued by Ii Naomasa until the latter was incapacitated by a shot from a rifleman.
The Western Army forces continued to crumble without the arrival of reinforcements, further complicated by the waves of defections, until the battle had finally concluded. Historian Andō Yūichirō estimated that the battle in Sekigahara took place in its entirety over a mere 2 hours – from 10 am to noon – contrary to the Edo-period accepted theory of the battle lasting twice as long.

### Late arrivals

The combined Eastern Army forces of Tokugawa Hidetada and Sakakibara Yasumasa, who commanded as many as 38,000 soldiers, were at the time of the battle bogged down in the Siege of Ueda against Sanada Masayuki. At the same time, 15,000 Western Army soldiers were being held up by 500 troops under Hosokawa Yūsai in the Siege of Tanabe in Maizuru, many of the former refusing to advance out of their respect for the Hosokawa. Due to these incidents, large proportions of both armies' forces ultimately never participated in the clash at Sekigahara.
Another Western Army contingent that failed to reach the Sekigahara battlefield was led by Tachibana Muneshige, who had been stalled by Kyōgoku Takatsugu in the Siege of Ōtsu. As result, Muneshige was forced to remain at Osaka Castle after learning of the Western Army's annihilation at Sekigahara. However, when Mōri Terumoto (also at Osaka Castle) offered his surrender to the Eastern Army, Muneshige departed with his army and returned to his homeland in Kyushu.

## Aftermath

As soon as the news of the Eastern Army's victory at Sekigahara reached Ogaki Castle, which at the time was still besieged by Mizuno Katsunari, Western Army-affiliated garrison commander Akizuki Tanenaga immediately surrendered and opened the castle for Katsunari. In response, Katsunari immediately wrote to Ii Naomasa asking that Ieyasu pardon Tanenaga, which Ieyasu accepted.
The most prominent political effect of the Eastern Army victory in Sekigahara was the shifting authority to assign military ranks and redistribute lands from the Toyotomi clan to Tokugawa Ieyasu. Immediately following the battle, Ieyasu redistributed domains worth 6.8 million koku, primarily as recompense for the allies instrumental in his victory:
* Ikeda Terumasa was reassigned from Mikawa Province, Yoshida region to a 520,000-koku domain in Harima Province, Himeji region
* Tōdō Takatora was reassigned to a 200,000-koku domain in Imabari, Ehime
* Matsudaira Tadayoshi was reassigned from a 100,000-koku domain in Musashi Province, Yuki region, to a 520,000-koku domain in Echizen Province, Fukui region
* Yūki Hideyasu was reassigned from a 101,000-koku domain in Shimōsa Province, Shinobu region, to a 569,000-koku domain in Owari Province, Kiyosu region
* Gamō Hideyuki was reassigned from a 180,000-koku domain in Shimotsuke Province, Utsunomiya region, to a 600,000-koku domain in Mutsu Province, Aizu region
* Maeda Toshinaga had his 835,000-koku domain in Kaga Province, Kanazawa region, expanded to 1,100,000 koku
* Katō Kiyomasa had his 195,000-koku domain in Higo Province, Kumamoto region, expanded to 515,000 koku
* Kuroda Nagamasa was reassigned from a 180,000-koku domain in Buzen Province, Nakatsu region, to a 523,000-koku domain in Chikuzen Province, Fukuoka region
* Fukushima Masanori had his 200,000-koku domain in the area of contemporary Aki District, Hiroshima, expanded to 498,000 koku
* Horio Tadauji had his domains in Matsue, Izumo, expanded to 240,000 koku
* Ieyasu also bestowed increases of at least into 10,000 koku to many of his fudai daimyō (Tokugawa clan hereditary vassals) whose domain were less than 10,000 koku before the battle.
Notably, Kobayakawa Hideaki, whose defection from the Western Army contributed greatly to Ieyasu's victory, was bestowed a domain which covered parts of Bizen Province and Mimasaka Province and which was worth 520,000 koku. Perhaps surprisingly, Ieyasu bestowed only meager domain increases to the three remaining Shitennō (Ii Naomasa, Honda Tadakatsu, and Sakakibara Yasumasa), his closest high-ranking generals, as compared to those he offered to newer commanders and vassals. However, it is possible this perceived disparity was the result of those generals choosing to decline Ieyasu's offers of extensive compensation.
As for the generals of the defeated Western Army, roughly 87 daimyō had their domains confiscated and their power stripped due to their support of Mitsunari in the battle. The long-standing Chōsokabe clan, headed by Chōsokabe Morichika, was stripped of its title and domain of Tosa Province, which was consequently given to Yamauchi Kazutoyo in recognition of his service to the Tokugawa. Several former Chōsokabe retainers resisted the forcible takeover by the Tokugawa and Yamauchi; in response, Ii Naomasa sent military reinforcements to assist Kazutoyo in suppressing the rebellion of Chōsokabe vassals in Tosa. Suzuki Hyōe, vassal of Naomasa, relieved Kazutoyo with an army transported by 8 ships, ultimately pacifying the region in 5 weeks after killing about 273 enemies.
On September 17, Ieyasu dispatched his army, led by Kobayakawa Hideaki, to attack Sawayama Castle in Ōmi Province, the home base of Mitsunari. Most of the castle's troops had been sent to Sekigahara, leaving the castle's garrison with only 2,800 men. Despite Mitsunari's absence, the defense of the castle was initially successful under the leadership of Mitsunari's father Ishida Masatsugu and brother Masazumi. Following the defection of retainer Moritomo Hasegawa and other defenders, the castle was opened to the besieging army; most of Mitsunari's relatives, including Masatsugu, Masazumi, and Mitsunari's wife Kagetsuin, were killed in battle or committed suicide.
In response to Shimazu Yoshihiro's support of the Western Army, Ieyasu prepared a massive punitive expedition to Kyushu, to be led by his son Tokugawa Hidetada. This force was to be composed of Eastern Army forces thereupon engaged in the West, including the armies of Katō Kiyomasa, Kuroda Yoshitaka, Nabeshima Naoshige, and the Tachibana clan. However, this operation was aborted once Shimazu Yoshihisa, the head of the Shimazu clan, entered negotiations with Ieyasu. Shimazu-Tokugawa deliberations continued until 1602 and were aided by the intercession of Kiyomasa, Yoshitaka, and Tachibana Muneshige; ultimately, the Shimazu clan avoided punishment, becoming the only Western Army-aligned clan to avoid losing territory after the defeat at Sekigahara.
On November 6, Ishida Mitsunari, Konishi Yukinaga and Ankokuji Ekei were captured and executed.
In 1603, Ieyasu was officially appointed as shōgun by Emperor Go-Yōzei; as such, the conclusion of the Battle of Sekigahara has served as the de facto beginning of the Edo period, and more generally, of the return of stability to Japan. In 1664, Hayashi Gahō, Tokugawa historian and rector of Yushima Seidō, wrote:
   Evil-doers and bandits were vanquished and the entire realm submitted to Lord Ieyasu, praising the establishment of peace and extolling his martial virtue. That this glorious era that he founded may continue for ten thousands upon ten thousands of generations, coeval with heaven and earth.
In 1931, the location of the battle was registered as a Monument of Japan. The positions of Ieyasu and Mitsunari's armies, and that of the death of Ōtani Yoshitsugu, are commemorated therein.

## Statistics and chronology

Commanders :
| Commanders of Eastern Army (Tokugawa Force) | Commanders of Western Army (Ishida Force) |
| Tokugawa Ieyasu (head of the alliance): 30,000 men Maeda Toshinaga Date Masamune Katō Kiyomasa: 3,000 men Fukushima Masanori: 6,000 men Hosokawa Tadaoki: 5,000 men Numata Jakō Asano Yoshinaga: 6,510 men Ikeda Terumasa: 4,560 men Kuroda Nagamasa: 5,400 men Katō Yoshiaki: 3,000 men Komatsuhime Tanaka Yoshimasa [ja]: 3,000 men Tōdō Takatora: 2,490 men Sanada Nobuyuki Mogami Yoshiaki Yamauchi Kazutoyo: 2,058 men Hachisuka Iemasa Honda Tadakatsu: 500 men Terazawa Hirotaka: 2,400 men Ikoma Kazumasa: 1,830 men Ii Naomasa: 3,600 men Matsudaira Tadayoshi: 3,000 men Oda Nagamasu: 450 men Tsutsui Sadatsugu: 2,850 men Kanamori Nagachika: 1,140 men Tomita Nobutaka [ja]: 1,300 men Yuki no Kata Okaji no Kata Furuta Shigekatsu: 1,200 men Wakebe Mitsuyoshi [ja] Horio Tadauji Nakamura Kazutada [ja] Arima Toyouji [ja] 900 men Kyōgoku Takatomo: 3,000 men Kuki Moritaka | Mōri Terumoto (official head of the alliance) (not present) Ishida Mitsunari (de facto head of the alliance): 4,000 men Niwa Nagashige Uesugi Kagekatsu Maeda Toshimasa (Brother of Maeda Toshinaga) Ukita Hideie: 17,000 men Shimazu Yoshihiro: 1,500 men Kobayakawa Hideaki (defected): 15,600 men Konishi Yukinaga: 4,000 men Mashita Nagamori Ogawa Suketada (defected): 2,100 men Ōtani Yoshitsugu: 600 men Ōtani Yoshiharu [ja]: 3,500 men Wakisaka Yasuharu (defected): 990 men Ankokuji Ekei: 1,800 men Satake Yoshinobu Oda Hidenobu Chōsokabe Morichika: 6,600 men Kutsuki Mototsuna (defected): 600 men Akaza Naoyasu (defected): 600 men Kikkawa Hiroie (defected): 3,000 men Natsuka Masaie: 1,500 men Mōri Hidemoto: 15,000 men Tachibana Ginchiyo Toda Katsushige: 1,500 men Sanada Masayuki Sanada Yukimura: 40 Shima Sakon: 1,000 men Gamō Yorisato [ja]: 1,000 men Shimazu Toyohisa: 750 men Kuki Yoshitaka Vassals of the Toyotomi: 2,000 men |
The participants of the Battle of Sekigahara are listed below, with corresponding troop count estimates (in tens of thousands): ○ = Main daimyō who participated in the Battle of Sekigahara
● = Daimyō who defected
| | Daimyō | Kokudaka (hundreds) | | Daimyō | Kokudaka (hundreds) |
| Western Army | Mōri Terumoto | 121.0 | Eastern Army | Tokugawa Ieyasu ○ | 256.0 |
| Western Army | Uesugi Kagekatsu | 120.0 | Eastern Army | Maeda Toshinaga | 84.0 |
| Western Army | Satake Yoshinobu | 54.0 | Eastern Army | Date Masamune | 58.0 |
| Western Army | Shimazu Yoshihiro ○ | 73.0 | Eastern Army | Katō Kiyomasa | 20.0 |
| Western Army | Ukita Hideie ○ | 57.0 | Eastern Army | Fukushima Masanori ○ | 24.0 |
| Western Army | Ishida Mitsunari ○ | 19.4 | Eastern Army | Hosokawa Tadaoki ○ | 18.0 |
| Western Army | Konishi Yukinaga ○ | 20.0 | Eastern Army | Asano Yoshinaga ○ | 16.0 |
| Western Army | Mashita Nagamori | 20.0 | Eastern Army | Ikeda Terumasa ○ | 15.0 |
| Western Army | Ogawa Suketada ● | 7.0 | Eastern Army | Kuroda Nagamasa ○ | 18.0 |
| Western Army | Ōtani Yoshitsugu ○ | 5.0 | Eastern Army | Katō Yoshiaki ○ | 10.0 |
| Western Army | Wakisaka Yasuharu ● | 3.0 | Eastern Army | Tanaka Yoshimasa ○ | 10.0 |
| Western Army | Ankokuji Ekei ○ | 6.0 | Eastern Army | Tōdō Takatora ○ | 11.0 |
| Western Army | Kobayakawa Hideaki ● | 37.0 | Eastern Army | Mogami Yoshiaki | 24.0 |
| Western Army | Oda Hidenobu | 13.5 | Eastern Army | Yamauchi Kazutoyo ○ | 6.0 |
| Western Army | Chōsokabe Morichika ○ | 22.0 | Eastern Army | Hachisuka Yoshishige | 17.7 |
| Western Army | Kutsuki Mototsuna ● | 2.0 | Eastern Army | Honda Tadakatsu ○ | (10.0) |
| Western Army | Akaza Naoyasu ● | 2.0 | Eastern Army | Terazawa Hirotaka ○ | 8.0 |
| Western Army | Kikkawa Hiroie ● | (14.2) | Eastern Army | Ikoma Kazumasa ○ | 15.0 |
| Western Army | Natsuka Masaie ○ | 5.0 | Eastern Army | Ii Naomasa ○ | (12.0) |
| Western Army | Mōri Hidemoto ○ | (20.0) | Eastern Army | Matsudaira Tadayoshi ○ | 13.0 |
| Western Army | Toda Katsushige ○ | 1.0 | Eastern Army | Tsutsui Sadatsugu ○ | 20.0 |
| Western Army | Sanada Masayuki | 4.0 | Eastern Army | Kyōgoku Takatomo ○ | 10.0 |
Below is a chronology of the events leading up to and shortly following the Battle of Sekigahara:
* May 7 – Ieyasu asks Uesugi Kagekatsu for explanations for his military mobilization. Kagekatsu refuses Ieyasu.
* June 8 – Ieyasu calls his allies to punish the Uesugi.
* July 12 – Ieyasu holds a meeting in Osaka to plan the punishment of the Uesugi, attended by Hosokawa Tadaoki, Date Masamune, Mogami Yoshiaki, Satake Yoshinobu and Nanbu Toshinao.
* July 26 – Ieyasu leaves Fushimi Castle after meeting with Torii Mototada.
* August 16 – Mitsunari meets with Ōtani Yoshitsugu and convinces him to take sides against the Tokugawa.
* August 17 – Ishida Mitsunari, Ankokuji Ekei, Ōtani Yoshitsugu and Mashita Nagamori meet in Sawayama and agree to ask Mōri Terumoto to become commander in chief of the alliance. Nagamori secretly sends Ieyasu news about the meeting.
* August 19 – Siege of Tanabe: while Hosokawa Tadaoki's army was en route to attack Uesugi and Mitsunari's Western Army, Ikoma Chikamasa's forces under Onoki Shigekatsu attack Tanabe Castle against Hosokawa Fujitaka.
* August 22 – Mōri Terumoto arrives at Osaka Castle and takes command of the Western Army.
* August 23 – Battle of Gifu Castle: Western-aligned Oda Hidenobu is besieged and defeated by Ikeda Terumasa, Ikeda Sen and Fukushima Masanori of the Eastern Army.
* August 27 – Siege of Fushimi, led by Mitsunari and Kobayakawa Hideaki.
* August 29 – Ieyasu establishes his headquarters in Oyama, Shizuoka to discuss strategy with allies.
* August 30 – Battle of Asai: Maeda Toshinaga of the Eastern Army holds back the forces of Niwa Nagashige and Uesugi Kagekatsu.
* September 1 – Siege of Shiroishi: Uesugi Kagekatsu loses Shiroishi Castle to Date Masamune's pro-Tokugawa troops.
* September 6 – Fall of Tanabe Castle to the Western Army. Fujitaka enters Kameyama Castle, governed by Maeda Shigekatsu in Tanba.
* September 7 – Tokugawa ally Maeda Toshinaga attacks his brother, Toshimasa, and besieges Daishoji Castle. The commander of the garrison, Yamaguchi Munenaga, commits seppuku.
* September 8 – Fall of Fushimi Castle: Torii Mototada and Matsudaira Ietada die.
* September 10 – Ieyasu returns to Edo Castle from Oyama.
* September 15 – Mitsunari's Western army arrives at Ogaki Castle.
* September 29 – Nabeshima Naoshige and other Western Army generals besiege Matsuoka Castle. The Eastern Army occupies the heights of Akasaka, near Ogaki Castle.
* September 29 – Fall of Gifu Castle to the Eastern Army. Tokugawa Hidetada heads towards Nakasendo.
* September 30 – Mōri Hidemoto lays siege to Anotsu Castle, held by Tomita Nobutaka.
* October 1 – Mitsunari returns to Sawayama Castle from Ogaki, asking Terumoto to march. Terumoto has been at Osaka Castle defending Toyotomi Hideyori.
* October 7 – Ieyasu leaves Edo with 30,000 men heading towards Tokaido.
* October 9 – Tokugawa Hidetada reaches Komoro, Nagano, and against the orders of his father, diverts his forces towards Ueda.
* October 12 – Ieyasu passes through Shimada in Suruga. Hidetada camps in Sometani village to besiege Ueda Castle, held by Sanada Masayuki.
* October 13 – Ieyasu passes through Nakaizumi in Tōtōmi. Mōri Hidemoto and Kikkawa Hiroie enter Mino and set up camp near Mount Nangu. Western Army commanders Mōri Hidekane, Tachibana Muneshige and Tsukushi Hirokado besiege Ōtsu Castle, held by Kyōgoku Takatsugu.
* October 14 – Ieyasu receives a secret messenger from Kobayakawa Hideaki, who offers him support. Naoe Kanetsugu leads the Uesugi forces against Mogami Yoshiaki at the Siege of Hasedo.
* October 16 – Hidetada abandons the Siege of Ueda Castle and heads to Mino.
* October 19 – Ieyasu arrives at Gifu Castle in Mino. Kuroda Yoshitaka defeats Ōtomo Yoshimune and other Ishida-allied generals at the Battle of Ishigakibara.
* October 20 – Ieyasu moves to Akasaka. The two coalitions make contact at Kuisegawa, near Akasaka. The Eastern force retreats to Sekigahara. The Western coalition heads to Sekigahara from Ogaki Castle.
* October 21 – Battle of Sekigahara
* October – Siege of Yanagawa: the last battle of the Kyūshū Sekigahara Campaign.
* October 30 – Date Masamune tries to conquer Fukushima Castle but fails and retreats. (In May 1601, during the Battle of Matsukawa, Masamune is repelled by Honjō Shigenaga.)
* November 5 – Naoe Kanetsugu calls for a full withdrawal of all Uesugi forces, putting an end to Uesugi's campaigns in the north.

## Cultural depictions

Owing to its pivotal status as the climax of the Sengoku period, the Battle of Sekigahara is a common subject of modern depictions and retellings:
* In 1966, Ryōtarō Shiba authored the historical novel Sekigahara, which has since been adapted into a 2017 film of the same name directed by Masato Harada.
* James Clavell included a historical-fiction depiction of the battle in his 1975 novel Shōgun, later adapted for television in the United States as a miniseries in 1980 and again as a series in 2024.
* Tokyo Broadcasting System aired a television miniseries about the battle in January 1981, also entitled Sekigahara [ja].
* The 2000 real-time tactics video game Kessen is set during the conflict between the Tokugawa and Toyotomi clans, and features the Battle of Sekigahara.
* The 2011 grand strategy video game Total War: Shogun 2 includes Sekigahara as a historical battle, in which the player controls Mitsunari's Western Army.
* The 2017 action RPG video game Nioh portrays events related to the battle.