Battle of Sekigahara

The Battle of Sekigahara (Shinjitai: 関ヶ原の戦い; Kyūjitai: 關ヶ原の戰い) was a decisive battle on October 21, 1600 (Keichō 5, 15th day of the 9th month) which cleared the path to the Shogunate for Tokugawa Ieyasu. Though it would take three more years for Ieyasu to consolidate his position of power over the Toyotomi clan and the daimyo, Sekigahara is widely considered to be the unofficial beginning of the Tokugawa bakufu, the last shogunate to control Japan. Japan had a long period of peace after the battle.

Background
Oda Nobunaga controlled the last Shogun Ashikaga Yoshiaki from behind the scenes since commoners could not hold the position. Ashikaga tried to escape this predicament in 1573 by attacking Oda, but failed and was exiled, thus ending his shogunate. This left the army under control of Oda, although he was not shogun. When his own retainer Akechi Mitsuhide attempted to assassinate him in 1582, Oda killed himself. This left the majority of the army in the control of his subordinate Toyotomi Hideyoshi. Since the Toyotomi clan was known to be descended from peasant stock, neither Hideyoshi nor his heir Hideyori would be recognized or accepted as shogun.

Even though Toyotomi Hideyoshi unified Japan and consolidated his power following the Siege of Odawara in 1590, his failures in his invasions of Korea significantly weakened the Toyotomi clan's power as well as the support of the loyalists and bureaucrats that continued to serve and support the Toyotomi clan after Hideyoshi's death during the second invasion. Hideyoshi's and his brother Hidenaga's presence kept the two main factions of the time, which rallied behind Ishida Mitsunari and Tokugawa Ieyasu respectively, from anything more than quarreling, but when both of them died, the conflicts were exacerbated and developed into open hostilities. With no appointed shogun over the armies, this left a power vacuum in the Japanese government.

Most notably, Katō Kiyomasa and Fukushima Masanori were publicly critical of the bureaucrats, especially Ishida Mitsunari and Konishi Yukinaga. Tokugawa Ieyasu took advantage of this situation, and recruited them, redirecting the animosity to weaken the Toyotomi clan.

Beginning
Tokugawa Ieyasu was no longer rivaled in terms of seniority, rank, reputation and overall influence within the Regency of the Toyotomi clan after the death of Regent Maeda Toshiie. Rumors started to spread stating that Ieyasu, at that point the only surviving ally of Oda Nobunaga, would take over Hideyoshi's legacy just as Nobunaga's was taken. This was especially evident amongst the loyalist bureaucrats, who suspected Ieyasu of agitating unrest amongst Toyotomi's former vassals.

Later, a supposed conspiracy to assassinate Ieyasu surfaced, and many Toyotomi loyalists, including Toshiie's son, Toshinaga, were accused of taking part and forced to submit to Ieyasu's authority. However, Uesugi Kagekatsu, one of Hideyoshi's appointed regents, defied Ieyasu by building up his military. When Ieyasu officially condemned him and demanded that he come to Kyoto to explain himself before the Emperor, Kagekatsu's chief advisor, Naoe Kanetsugu responded with a counter-condemnation that mocked Ieyasu's abuses and violations of Hideyoshi's rules, in such a way that Ieyasu was infuriated.

Afterwards, Ieyasu summoned the help of various supporters and led them northward to attack the Uesugi clan. Many of them were at that moment were besieging Hasedō though. Ishida Mitsunari, grasping the opportunity created by the chaos, rose up in response and created an alliance to challenge Ieyasu's supporters.

Troop deployment
Mitsunari, in his home Sawayama Castle, met with Ōtani Yoshitsugu, Mashita Nagamori, and Ankokuji Ekei. Here, they forged the alliance, and invited Mōri Terumoto, who actually did not take part in Sekigahara, to be its head. Thus formed what came to be referred to as the Western Army. Mori seized Osaka Castle for their base of operations, since most of Tokugawa’s forces had vacated the area to attack Uesugi.

Ishida wanted to reinforce Mori at the impregnable Osaka Castle. This would let Mitsunari control the traditional capital city of Kyoto and challenge Tokugawa’s power. To this end, Mitsunari’s forces headed for Gifu Castle in order to use it as a staging area to move on Kyoto, since it was controlled by his ally Oda Hidenobu.

Back in Edo, Ieyasu received news of the situation in the Kansai region and decided to deploy his forces. Tokugawa himself commanded 30,000 men and his subordinates led another 40,000 men. This made up the bulk of what would later be called the Eastern Army. He had some former Toyotomi daimyo engage with the Western Army, while he split his troops and marched west on the Tōkaidō towards Osaka.

Since Tokugawa and his army were departing from Edo, they could only take two roads, both of which converged on Gifu Castle. Tokugawa marched on Gifu while Ishida was delayed at Fushimi Castle. This fortress was a halfway point between Osaka and Kyoto and was controlled by Tokugawa’s ally Torii Mototada. Ishida could not risk leaving a force that could attack his rear, so he marched on it. It took him ten days to capture Fushimi, and in that time Tokugawa had taken Gifu Castle. This forced Ishida Mitsunari to retreat southward in the rain. Tired from a day’s march and their gunpowder wet from the rain, Ishida and his forces stopped at Sekigahara. “Ishida deployed his troops in a strong defensive position, flanked by two streams with high ground on the opposite banks.” His right flank was reinforced by daimyo Kobayakawa Hideaki on Mount Matsuo. On October 20, 1600, Tokugawa learned that Ishida had deployed his troops at Sekigahara in a defensive position. They had been following the Western Army, and benefited from considerably better weather. At dawn of the next day, Tokugawa’s advanced guard stumbled into Ishida’s army. Neither side saw each other due to the dense fog caused by the earlier rain. Both sides panicked and withdrew, but this resulted in both sides being aware of their adversary’s presence. Ishida held his current defensive position and Tokugawa deployed his own forces. He sent his allies’ forces in a line to the front, and held his own troops in reserve. Around 8AM, wind blew away the fog, and both sides noticed their respective adversary’s positions. Last-minute orders were issued and the battle began.

The battle
Initially, Ieyasu's eastern army had 75,000 men, while Mitsunari's western army numbered 120,000. Tokugawa had also sneaked in a supply of arquebuses. Knowing that Ieyasu was heading toward Osaka, Mitsunari decided to abandon his positions and marched to Sekigahara. Even though the Western forces had tremendous tactical advantages, Ieyasu had already been in contact with many daimyo in the Western Army for months, promising them land and leniency after the battle should they switch sides.

Tokugawa’s forces started the battle when Fukushima Masanori, the leader of the advanced guard, charged north from Tokugawa’s left flank along the Fuji River against the Western Army’s right center. The ground was still muddy from the previous day's rain, so the conflict there devolved into something more primal. Tokugawa then ordered attacks from his right and his center against the Western Army’s left in order to support Fukushima’s attack.

This left the Western Army’s center unscathed, so Ishida ordered this unit under the command of Shimazu Yoshihiro to reinforce his right flank. Shimazu refused as daimyo of the day only listened to respected commanders, which Ishida was not.

Fukushima’s attack was slowly gaining ground, but this came at the cost of exposing their flank to attack from across the Fuji River by Otani Yoshitsugu, who took advantage of this opportunity. Just past Otani’s forces were those of Kobayakawa Hideaki on Mount Matsuo.

Kobayakawa was one of the daimyo that had been courted by Tokugawa. Even though he had agreed to defect to Ieyasu's side, in the actual battle he was hesitant and remained neutral. As the battle grew more intense, Ieyasu finally ordered arquebuses to fire at Kobayakawa's position on Mount Matsuo in order to force Kobayakawa to make his choice. At that point Kobayakawa joined the battle as a member of the Eastern Army. His forces charged Otani's position, which did not end well for Kobayakawa. Otani’s forces had dry gunpowder, so they opened fire on the turncoats, making the charge of 16,000 men mostly ineffective. However, he was already engaging forces under the command of Tōdō Takatora, Kyogoku Takatsugu, and Oda Yuraku when Kobayakawa charged. At this point, the buffer Otani established was outnumbered. Seeing this, Western Army generals Wakisaka Yasuharu, Ogawa Suketada, Akaza Naoyasu, and Kutsuki Mototsuna switched sides, turning the tide of battle.

Fall of the Western Army


Heavily outnumbered, Otani had no choice but to retreat. This left the Western Army’s right flank wide open, so Fukushima and Kobayakawa began to roll up it. Thus Ishida’s right flank was destroyed and his center was being pushed back, so he decided to retreat.

Ishida’s only remaining forces were on Mount Nangu. However, these forces were there for a reason. Kikkawa Hiroie was one of the commanders on the mountain. Kikkawa's troops formed the front lines of the Mori army, which was commanded by his cousin Mori Hidemoto. Earlier, when Hidemoto decided to attack the Tokugawa forces, Hiroie refused to comply, stating he was busy eating and asked to be left alone. This in turn prevented the Chosokabe army, which deployed behind the Mori clan, from attacking. When Ishida arrived, Kikkawa betrayed him as well. He kept the Mori army at bay, and since Ishida had no more support, he was defeated.

The Western Army disintegrated afterwards, and the commanders scattered and fled. Some, like Ukita Hideie managed to escape, at least initially. Many others did not. Shima Sakon was shot and fatally wounded by a round from an arquebus and Ōtani Yoshitsugu committed suicide. Mitsunari, Yukinaga and Ekei were some of those who were captured and a few, like Mōri Terumoto and Shimazu Yoshihiro were able to return to their home provinces. Mitsunari himself would be executed.

Late arrivals
Both sides had forces that did not arrive at Sekigahara in time to participate due to other battles.

Ieyasu's son Hidetada led another group through Nakasendō. However, Hidetada's forces were bogged down as he attempted to besiege Sanada Masayuki's Ueda Castle against his father's direct orders. Even though the Tokugawa forces numbered some 38,000, an overwhelming advantage over the Sanada's mere 2,000, they were still unable to capture the strategist's well-defended position.

At the same time, 15,000 Toyotomi troops were being held up by 500 troops under Hosokawa Yusai at Tanabe Castle in present day Maizuru, Kyoto Prefecture. Some among the 15,000 troops respected Hosokawa so much they intentionally slowed their pace. Due to these incidents, a large number of Tokugawa- and Toyotomi-aligned troops failed to show up in time for the battle. Had either of these armies participated in the conflict, it could have ended quite differently.

Rise of the Tokugawa Shogunate


Tokugawa Ieyasu redistributed the lands and fiefs of the participants, generally rewarding those who assisted him and displacing, punishing, or exiling those who fought against him. In doing so, he gained control of many former Toyotomi territories. Tokugawa himself also became quite wealthy.

Following the public execution of Ishida Mitsunari, Konishi Yukinaga and Ankokuji Ekei, the influence and reputation of the Toyotomi clan and its remaining loyalists drastically decreased.

At the time, the battle was considered only an internal conflict between Toyotomi vassals. However, after Ieyasu was named Shogun in 1603 by Emperor Go-Yozei,  a position that had been left vacant since the fall of the Ashikaga shogunate 27 years earlier, the battle was perceived as a more important event. In 1664, Hayashi Gahō, Tokugawa historian and rector of Yushima Seido, summarized the consequences of the battle: "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."

Seeds of dissent from Sekigahara
While most clans were content with their new status, there were many clans, especially those on the western side, who became bitter about their displacement or what they saw as a dishonorable defeat or punishment. Three clans in particular did not take the aftermath of Sekigahara lightly:


 * The Mōri clan, headed by Mōri Terumoto, remained angry toward the Tokugawa shogunate for being displaced from their fief, Aki, and being relocated to the Chōshū Domain, even though the clan did not take part in the battle at all.


 * The Shimazu clan, headed by Shimazu Yoshihiro, blamed the defeat on its poor intelligence-gathering, and while they were not displaced from their home province of Satsuma, they did not become completely loyal to the Tokugawa shogunate either. Taking advantage of its large distance between Edo and the island of Kyūshū as well as its improved espionage, the Shimazu clan demonstrated that it was virtually an autonomous kingdom independent from the Tokugawa shogunate during its last days.


 * The Chōsokabe clan, headed by Chōsokabe Morichika, was stripped of its title and domain of Tosa and sent into exile. Former Chōsokabe retainers never quite came to terms with the new ruling family, the Yamauchi clan, which made a distinction between its own retainers and former Chōsokabe retainers, giving them lesser status as well as discriminating treatment. This class distinction continued even generations after the fall of the Chōsokabe clan.

The descendants of these three clans would in two centuries collaborate to bring down the Tokugawa shogunate, leading to the Meiji Restoration.

Trivia

 * Legend has it that the ronin Miyamoto Musashi was present at the battle among Ukita Hideie's army and escaped the defeat of Hideie's forces unharmed. Musashi would have been around 16 years of age at the time.  There is no hard evidence to prove if Musashi was present or not for the battle.
 * According to one account, the Musashi yuko gamei, "Musashi's achievements stood out from the crowd, and were known by the soldiers in all camps." Musashi is reticent on the matter, writing only that he had "participated in over six battles since my youth."

In popular culture

 * The related political intrigues leading up to the battle was the historical foundation for James Clavell's 1975 novel, Shōgun, later televised in 1980.
 * Re-enacted in the 2008 BBC Docudrama series Heroes and Villains.
 * This battle was figured in the manga and anime series Samurai Deeper Kyo.
 * This battle was figured in the manga Vagabond
 * This battle was featured as a campaign in Age of Empires III: The Asian Dynasties
 * The battle features as a playable "Historical Battle" in the 2011 real-time strategy game Total War: Shogun 2 in the side of Ishida Mitsunari.
 * The battle features heavily into the strategy video game Kessen.
 * This battle is depicted in Sengoku Basara: The Last Party.
 * The battle of Sekigahara is fictionalized in the Young Samurai series as the Battle of Nakasendo
 * The low-complexity block wargame Sekigahara: Unification of Japan, by GMT Games is based on Tokugawa's campaign, featuring an innovative card based combat system without using dice.
 * The battle of Sekigahara was featured in the Samurai Warriors 2 series.

Other reading
Paul Davis used the following sources to compile the chapter "Sekigahara, 21 October 1600" in 100 Decisive Battles: From Ancient Times to the Present "Sekigahara, 21 October 1600."
 * Sadler, A.L. The Maker of Modern Japan: The Life of Tokugawa Ieyasu London: George Allen & Unwin, 1937
 * Sansom, George. A History of Japan from 1334-1615 Stanford University Press, 1961
 * Turnbull, Stephen. The Samurai: A Military History New York: Macmillan, 1977