faction of Nanbu clan, felt that he had a stronger claim to the title of clan chieftain, and immediately rose in rebellion. In 1591, Hideyoshi and Ieyasu took the Kunohe Rebellion as a personal affront to Toyotomi authority and by mid-year organized a retaliatory army to retake northern Tōhoku and to restore the area to Nanbu Nobunao's control. Rise to Power (1591–1599) Daimyo of Kantō region In 1591, Ieyasu now gave up control of his five provinces (Mikawa, Tōtōmi, Suruga, Shinano, and Kai) and moved all his soldiers and vassals to his new eight provinces at the Kantō region. He himself occupied the castle town of Edo in Kantō. This was possibly the riskiest move Ieyasu ever made—to leave his home province and rely on the uncertain loyalty of the formerly Hōjō samurai in Kantō. In the end however, it worked out brilliantly for Ieyasu. He reformed the Kantō region, controlled and pacified the Hōjō samurai and improved the underlying economic infrastructure of the lands. Also, because Kantō was somewhat isolated from the rest of Japan, Ieyasu was able to maintain a unique level of autonomy from Toyotomi Hideyoshi's rule. Within a few years, Ieyasu had become the second most powerful daimyo in Japan. There is a Japanese proverb which likely refers to this event: "Ieyasu won the Empire by retreating." Korean Campaign In 1592, Toyotomi Hideyoshi invaded Korea as a prelude to his plan to attack China. The Tokugawa samurai never actually took part in this campaign, though in early 1593, Ieyasu himself was summoned to Hideyoshi's court in Nagoya (in Kyūshū, different from the similarly spelled city in Owari Province) as a military advisor and given command of a body of troops meant as reserves for the Korean campaign. He stayed in Nagoya off and on for the next five years. Despite his frequent absences, Ieyasu's sons, loyal retainers and vassals were able to control and improve Edo and the other new Tokugawa lands. In 1593, Toyotomi Hideyoshi fathered a son and heir, Toyotomi Hideyori. However, the cost of the Japanese invasions of Korea significantly weakened the Toyotomi clan's power in Japan. Council of Five Elders In 1598, with Toyotomi Hideyoshi's health clearly failing, Hideyoshi called a meeting that would determine the Council of Five Elders, who would be responsible for ruling on behalf of his son after his death. The five that were chosen as tairō (regent)