From 1470 to 1573, the province of Tosa was governed by the Ichijo, but, in the latter year, Motochika, head of the Chosokabe, one of the seven vassal families of the Ichijo, usurped the province, and then received orders from Oda Nobunaga to conquer the other three provinces of the island in the interests of Nobunaga's son.
He commissioned Uesugi Kagekatsu to attack the Sasa troops in rear while Maeda Toshiiye menaced them from the front; he told off Hachisuka to oppose the soldier-monks of Kii; he posted Sengoku Hidehisa in Awaji to hold in check the forces of Chosokabe Motochika, and he stationed Ukita Hideiye at Okayama to provide against the contingency of hostility on the part of the Mori family.
Motochika, believing that Hosokawa's ultimate intention was to elevate Sumimoto to the shogunate, in which event the latter's guardian, Nagateru, would obtain a large access of power, compassed the murder of Hosokawa, the kwanryo, and proclaimed Sumiyuki head of the Hosokawa house.
It was not until the month of November, 1584, that Chosokabe Motochika effectually brought the island of Shikoku under his sway, and thus became free to lead a strong army, including the monks of Kii province, against Osaka.
Thereupon Miyoshi Nagateru moved up from Shikoku at the head of a strong army, and, after a fierce conflict, Motochika and Sumiyuki were killed, and Sumimoto, then in his eleventh year, became chief of the Hosokawa family, receiving also the office of kwanryo. The Motochika faction, however, though defeated, were not destroyed.
Therefore he adopted three sons: the first, Sumiyuki, being the child of the regent, Fujiwara Masamoto; the second and third, Sumimoto and Takakuni, being kinsmen of his own. The first of these three was entrusted to Kasai Motochika; the last two were placed in the care of Miyoshi Nagateru. These guardians were Hosokawa's principal vassals in Shikoku, where they presently became deadly rivals.
Motochika obeyed, but on the death of Nobunaga and his son he constituted himself master of Shikoku until Hideyoshi deprived him of all save Tosa. From 1156 to 1581 the Kono family held the province of Iyo, but there is nothing of historical interest in their career. Connected with Kyushu are the families of Shoni, Otomo, Ryuzoji, Kikuchi and Shimazu.
Ieyasu placed himself in communication with Sasa Narimasa, in Echizen; with Chosokabe Motochika, in Shikoku, and with the military monks in the province of Kii. The programme was that Narimasa should raise his standard in Echizen and Kaga, and that Motochika, with the monks of Kii, should move to the attack of Osaka, so that Hideyoshi would be compelled to carry on three wars at the same time.
Orders were immediately issued to Mori, Kikkawa, Kohayakawa, and Chosokabe Motochika to assemble their forces for an oversea expedition, and in the mean while, Sengoku Hidehisa was despatched to Kyushu bearing a letter in which Hideyoshi, writing over his title of kwampaku, censured the Shimazu baron for having failed to pay his respects to the Imperial Court in Kyoto, and called upon him to do so without delay.