On 21 October 1600, the Battle of Sekigahara was fought in Japan between Ishida Mitsunari and Tokugawa Ieyasu during the Sengoku Period.
Why did it happen?
Following the end of the Imjin War in 1598, Toyotomi Hideyoshi died and left Japan under the rule of his five-year-old son, Toyotomi Hideyori. Although regents were appointed to rule on Hideyori’s behalf until he came of age, two factions emerged: a coalition of generals under Ishida Mitsunari, and Tokugawa Ieyasu, who controlled most of eastern Japan. In 1600, while Tokugawa was distracted by a rebellion in eastern Japan, Ishida Mitsunari marched north to besiege several important castles and challenge Tokugawa’s power. When Tokugawa occupied a strategically important position at Mino Akasaka, Ishida withdrew to the narrow valley of Sekigahara, where he awaited Tokugawa, who had to defeat Ishida to strike at his power base in western Japan.
Who was involved?
Both the armies of Tokugawa Ieyasu and Ishida Mitsunari were 70,000 and 80,000 strong, respectively and consisted of samurai swordsmen, ashigaru spearmen, cavalry, arquebusiers, and artillery. The frontline of Tokugawa’s army consisted of samurai, ashigaru spearmen, arquebusiers and artillery under the command of Ii Naomasa on the right wing and Fukushima Masanori on the left wing. In the second line stood the cavalry while Tokugawa Ieyasu held troops in reserve. On the other side, Ishida Mitsunari and Shimazu Yoshiro commanded the left wing, which consisted of cavalry, arquebusiers and artillery. In the centre, under Konishi Yukinaga, stood samurai, and ashigaru spearmen, flanked on their right by arquebusiers, more ashigaru spearmen and cavalry under Otani Yoshitsugu. In addition, Mori Hidemoto commanded the reserves, while Kobayakawa Hideaki was positioned with 15,000 men on Mount Matsuo, ready to help either side by attacking the other in the flank.
What happened?
On 21 October at 8 am, Ishida’s arquebusiers under Ukita Hideie opened the battle by firing upon Ii Naomasa’s troops which pushed them back before Tokugawa rallied them. Tokugawa then ordered his samurai and ashigaru spearmen to charge Ishida Mitsunari himself, followed by his cavalry against Ishida’s centre. With all the main divisions engaged, both sides then signalled Kobayakawa Hideaki on Mount Matsuo to join them. When Tokugawa fired upon him with his artillery, Kobayakawa responded by attacking Ishida’s right flank. As Tokugawa renewed his attack all along the line, Kobyakawa swept through the rear of Ishida’s army and attacked Konishi Yukinaga from behind. At that point, morale in Ishida’s army dropped, and the army began to break up. At the same time, Shimazu Yoshiro cut his way through Tokugawa’s army with 80 samurai towards Tokugawa’s reserves, where Shimazu realised the battle was lost. Having lost 32,000 men, Ishida, and his reserves retreated, giving victory to Tokugawa, who lost 8,000 men.
What changed as a result?
The Battle of Sekigahara was a decisive victory for Tokugawa Ieyasu. In the aftermath of the battle, Tokugawa and Kobaykawa laid siege to the castle of Sawayama, which led to the capture and execution of Ishida Mitsunari. In 1603, Tokugawa declared himself shogun, despite opposition from the remaining supporters of Toyotomi Hideyori. In 1614, thousands of Toyotomi loyalists packed themselves into Osaka Castle, which Tokugawa besieged the following year. After defeating the loyalists in battle outside Osaka Castle, Toyotomi Hideyori burnt the castle and committed suicide, thus bringing the Sengoku Period to an end. Tokugawa Ieyasu died in 1616, but the Tokugawa Shogunate ruled Japan in isolation from the rest of the world until 1868, when the Meiji Restoration reinstated the emperor to power.
Bibliography
Grant, R.G. 1001 Battles That Changed the Course of History. London, Cassell Illustrated, 2011.
Holmes, Richard. & Marix Evans, Martin. A Guide to Battles: Decisive Conflicts in History. Oxford, Oxford University Press, 2009.
Overy, Richard. A History of War in 100 Battles. London, William Collins, 2014.
Webb, Jonathan. “Battle of Sekigahara, 1600.” The Art of Battle. Last revised 2015. http://www.theartofbattle.com/battle-of-sekigahara-1600/