Uesugi Kagekatsu
War 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.