Fukushima Masanori
Nearly all of Japan's daimyo and samurai now split into two factions—the Western Army (Mitsunari's group) and the Eastern Army (the anti-Mitsunari group). Ieyasu supported the anti-Mitsunari group, and formed them as his potential allies. Ieyasu's allies were Katō Kiyomasa, Fukushima Masanori, Date Masamune, the Kuroda clan, the Hosokawa clan and many daimyo from eastern Japan. Mitsunari allied himself with the three other regents: Ukita Hideie, Mōri Terumoto, and Uesugi Kagekatsu as well as Ōtani Yoshitsugu, Chosokabe clan, Shimazu clan and many daimyo from the western end of Honshū.