became imminent when Uesugi Kagekatsu, one of Hideyoshi's appointed regents, defied Ieyasu by building up his military at Aizu. When Ieyasu officially condemned him and demanded that he come to Kyoto to explain himself, Kagekatsu's chief advisor, Naoe Kanetsugu, responded with a counter-condemnation that mocked Ieyasu's abuses and violations of Hideyoshi's rules, and Ieyasu was infuriated. In July 1600, Ieyasu was back in Edo and his allies moved their armies to defeat the Uesugi clan, which they accused of planning to revolt against Toyotomi administration. On September 8, Ieyasu received information that Mitsunari had captured Fushimi castle and his allies had moved their army against Ieyasu. Ieyasu held a meeting with the Eastern Army daimyo, and they agreed to follow Ieyasu. Later on September 15, Mitsunari's Western army arrived at Ogaki Castle. On September 29, Ieyasu's Eastern Army took Gifu Castle. On October 7, Ieyasu and his allies marched along the Tōkaidō, while his son Hidetada went along through Nakasendō with 38,000 soldiers (a battle against Sanada Masayuki in Shinano Province delayed Hidetada's forces, and they did not arrive in time for the main Battle of Sekigahara). On October 20, Ieyasu's Eastern Army met Mitsunari's Western Army at Sekigahara, and on the following morning the battle began. Battle of Sekigahara The Battle of Sekigahara was the biggest and one of the most important battles in Japanese feudal history. It began on October 21, 1600. Initially, the Eastern Army led by Tokugawa Ieyasu had 75,000 men, while the Western Army numbered 120,000 men under Ishida Mitsunari. Ieyasu had also snuck in a supply of arquebuses. Knowing that the Tokugawa forces were heading towards Osaka, Mitsunari decided to abandon his positions and marched to Sekigahara. Even though the Western Army had tremendous tactical advantages, Ieyasu had already been in contact with many of the daimyo in the Western Army for months, promising them land and leniency after the battle should they switch sides, also having secretly communicated with Toyotomi Hideyoshi's nephew, Kobayakawa Hideaki. With a total of 170,000 soldiers facing each other, the Battle of Sekigahara ensued and ended with a complete Tokugawa victory. Later, the Western bloc was crushed and over the next few days Ishida Mitsunari and many other western nobles were captured and killed. Tokugawa Ieyasu was now the de facto ruler of Japan. Immediately after the victory at Sekigahara, Ieyasu redistributed land to the vassals who had served