Born the eldest son of Hōjō Ujitsuna; his grandfather was Hōjō Sōun (Ise Sōzui).
At 15, in his first battle, he defeated the Ōgigayatsu Uesugi at Ozawahara.
His father Ujitsuna died and he became head of the Hōjō at 26. His father reportedly left him precepts on caring for retainers and people, such as "after victory, tighten your helmet strings".
He launched a night attack with far fewer men on the great Uesugi-Ashikaga army besieging Kawagoe castle and won a decisive victory (troop numbers debated), making the Hōjō the leading power in the Kantō.
For peasants suffering from famine and earthquakes, he consolidated and lightened various levies, and carried out land surveys to put his domain's government in order.
He drove the Kantō deputy Uesugi Norimasa out of Kōzuke. Norimasa turned to Nagao Kagetora (Uesugi Kenshin) of Echigo, the root of a long war with Kenshin.
He allied with Takeda Shingen and Imagawa Yoshimoto, marrying his daughter to Imagawa Ujizane while his son Ujimasa wed Shingen's daughter.
He passed headship to his son Ujimasa but kept real power, and had the Odawara-shū Shoryō Yakuchō compiled, a register of retainers' lands and duties.
Uesugi Kenshin led the Kantō lords to besiege Odawara castle. Ujiyasu held out inside, and Kenshin withdrew after about a month.
When Takeda Shingen invaded Suruga and the three-way alliance collapsed, he allied with his long-time foe Uesugi Kenshin.
He died at Odawara castle at 56, reportedly advising his son Ujimasa to ally with the Takeda again. He is regarded as a wise ruler who firmly established Hōjō control of the Kantō.
Hōjō Sōun (Ise Sōzui)Hojo UjitsunaUesugi KenshinImagawa UjizaneTaigen SessaiHōjō UjimasaImagawa YoshimotoTakeda Shingen
Mōri MotonariFrancis XavierŌuchi YoshitakaMatsunaga HisahideImagawa YoshimotoImai SōkyūTakeda ShingenSue Harukata (Takafusa)
People of the Sengoku/Azuchi-Momoyama period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.