Battle of Sekigahara

The Battle of Sekigahara was fought on 21 October 1600, in what is now Gifu Prefecture in central Japan, between the forces of Tokugawa Ieyasu and a coalition of lords led by Ishida Mitsunari. Defections from Ishida's side turned the battle into a decisive Tokugawa victory. It is often called the most important battle in Japanese history, because it opened the way to the Tokugawa shogunate, which ruled Japan until 1868.

During the Sengoku period, Japan had been divided among warring regional lords, or daimyo, until Oda Nobunaga and then Toyotomi Hideyoshi reunified the country. When Hideyoshi died in 1598, during the costly invasions of Korea known as the Imjin War, his heir Hideyori was only five years old. Power was meant to be shared by a council of regents and senior administrators until the boy came of age. Tokugawa Ieyasu, the richest and most powerful of the regents, steadily extended his influence, arranging marriages and alliances against Hideyoshi's wishes. The death of the respected regent Maeda Toshiie in 1599 removed an important counterweight.

Opposition to Ieyasu gathered around Ishida Mitsunari, a capable administrator but unpopular with many of Hideyoshi's generals, several of whom bitterly resented him after quarrels during the Korean campaigns. In 1600 Ieyasu led an army east against the regent Uesugi Kagekatsu, who was arming in the north. Mitsunari used his absence to raise the so-called Western Army, with the great lord Mōri Terumoto as nominal commander, which took Osaka Castle, where Hideyori lived. Ieyasu turned back west with his Eastern Army, which included many former Toyotomi generals. His forces took the important Gifu Castle, and Mitsunari, fearing an attack on Osaka, chose to fight in the narrow valley of Sekigahara, where several roads met.

Each army probably numbered somewhere around 75,000 to 90,000 men, though figures differ widely between sources. On the morning of 21 October the two armies met in thick fog. When it lifted, the Eastern Army attacked, and for some time the Western Army held its ground. Several Western commanders, however, had already secretly agreed terms with Ieyasu. Troops of the Mōri clan, posted on a hill overlooking the battlefield, did not move. Kobayakawa Hideaki, a nephew of Hideyoshi by marriage who commanded a large force on another height, attacked his own allies under Ōtani Yoshitsugu, either at the start or partway through the fighting, which historians debate. Other commanders followed his lead, and the Western Army collapsed. Contemporary evidence suggests the battle lasted only a few hours. Losses are uncertain, but the defeated side suffered far more heavily.

Mitsunari fled but was captured and executed in Kyoto in November 1600 with other leaders of the coalition. Ieyasu confiscated or reduced the lands of those who had opposed him and rewarded his allies, reshaping the map of Japan's domains to his advantage. The so-called outside lords, or tozama, who had not been Tokugawa vassals before the battle, often kept large domains but were excluded from central government, while trusted hereditary vassals were placed in strategic positions.

In 1603 the emperor appointed Ieyasu shogun, and two years later he passed the title to his son Hidetada while keeping real control. The Toyotomi family survived at Osaka for some years, but Ieyasu destroyed it in the sieges of Osaka in 1614 and 1615. The Tokugawa shogunate, ruling from Edo, today's Tokyo, gave Japan more than two and a half centuries of internal peace.

Our 1600 map shows Japan at the time of the battle, and the 1650 map shows the country under the Tokugawa shogunate.