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.

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.

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 Hideyori'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: