Background
Upon his father"s death in 1541, a number of the Hōjō"s enemies sought to take advantage of the opportunity to seize major Hōjō strongholds.
北条 氏康北条 氏綱
Upon his father"s death in 1541, a number of the Hōjō"s enemies sought to take advantage of the opportunity to seize major Hōjō strongholds.
His only known wife was Imagawa Yoshimoto"s sister, Suikeiin. Two Uyesugi factions united with the Koga Kubo cause and attacked Kawagoye in 1542 in a night engagement still celebrated in Japanese military annals. "The result was the complete defeat of the Uyesugi forces and the Koga contingent.
From that date the Go-Hojo (Later Hojo) as they were called, went on to further triumphs, beginning with the destruction of the Uyesugi family." Ōgigayatsu Tomosada tried unsuccessfully to take Edo Castle (江戸城), and a few years later, in 1545, an army led by Ashikaga Haruuji (足利 晴氏) and Uesugi Norimasa (上杉 憲政) besieged Kawagoe Castle (see (1545)).
Ujiyasu slipped a samurai past the enemy lines to inform Tsunashige of the enemy"s approach, and made use of ninja to learn of the enemy"s strategy and attitude. Using this intelligence, he led a night attack against the Ashikaga/Uesugi force.
Despite being vastly outnumbered, the Hōjō army defeated the besiegers because, under Ujiyasu"s orders, they were not bulked down by heavy armor, and were not slowed down by seeking to take heads. This battle proved the end of the Ōgigayatsu Uesugi (扇谷上杉家) line and destroyed the prestige of Norimasa of the Yamanouchi Uesugi clan (山内上杉家) as the Governor-General of Kantō region (Kantō kanrei (関東管領)), until Uesugi Kenshin (上杉 謙信), who had subsequently been adopted by Norimasa, assumed the post in 1561.
He took Kōnodai in Shimōsa Province in 1564 following a battle against Satomi Yoshihiro (里見 義弘).
Towards the end of his life he saw the first major conflicts between his own clan and Takeda Shingen (武田 信玄), who would become one of the greatest warlords of the period. As a response to Hōjō"s intervention in his invasion of Suruga Province, Shingen came into Musashi Province from his home province of Kai, attacking Hachigata and Takiyama Castles, where Ujiyasu"s sons repulsed them. However, despite the intact castles behind him, Shingen pressed on to the Hōjō central home castle of Odawara (小田原城), burning the castle town and withdrawing after three days.
Two of Ujiyasu"s seven sons fought Takeda at the battle of Mimasetoge in 1569, ending the first of the Takeda campaigns against the Hōjō.
Turnbull, Stephen (2002). War in Japan: 1467-1615, Oxford: Osprey Publishing.