was a daimyà  (warlord) and third head of the Odawara Hà Âjà  clan. Known as the "Lion of Sagami", he was revered as a fearsome samurai and a cunning man. He is famous for his strategies of breaking the siege from Takeda Shingen and Uesugi Kenshin. A son of Hà Âjà  Ujitsuna (Ã¥ÂÂæ¡ æ°Â綱), his only known wife was Imagawa Yoshimoto's sister, Zuikei-in. Among his sons are Hà Âjà  Ujimasa and Uesugi Kagetora.
Born in 1515, his childhood name was Chiyomaru (Ã¥ÂÂ代丸). He fought his first battle when he was fifteen years old, facing Uesugi Tomooki of the à Âgigayatsu Uesugi clan (æÂÂè°·ä¸ÂæÂÂ家) at the Battle of Ozawahara in 1530.
Upon his father's death in 1541, a number of the later Hà Âjà Â's enemies sought to take advantage of the opportunity to seize major Hà Âjà  strongholds. Faced with almost endless warfare, Ujiyasu was compelled to reorganize the administration of the Hà Âjà  lands. He had already ordered a series of aggressive cadastral surveys between 1542 and 1543, and in 1550, he overhauled the Kandaka () taxation system.
Odawara, where his home castle Odawara Castle (å°Âç°åÂÂÃ¥ÂÂ) was located, was gradually transformed into an important trading center by modifying the region's throughways (which were hitherto designed with Kamakura as a hub) and creating an artisan's guild within the castle town. In addition, post stations and market places sprung up throughout the Hôjô's lands. Ujiyasu soon became one of the main powers in the Kantà  region.
In 1545, Uesugi Tomosada, of the à Âgigayatsu Uesugi clan and the eldest legitimate son of Uesugi Tomooki, attempted to regain Kawagoe Castle for the Uesugi clan. Tomosada allied himself with the Koga Kubo Ashikaga Haruuji (足å© æ´æ°Â) and Uesugi Norimasa (ä¸Âæ æ²æ¿) of the Yamauchi Uesugi clan (å±±å ä¸ÂæÂÂ家) and besieged Kawagoe Castle (Siege of Kawagoe Castle). The castle garrison, led by Hà Âjà  Tsunashige (Ã¥ÂÂæ¡ 綱æÂÂ), the stepson of Ujiyasu's brother Tamemasa (Ã¥ÂÂæ¡ çºæÂÂ) and son-in-law of Ujitsuna, was outnumbered 3,000 to allegedly 80,000 men. Ujiyasu, leading a relief force of 8,000 soldiers, slipped some 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 raid against the Ashikaga-Uesugi forces, which is now said to be one of the most notable examples of night fighting in samurai history. "The result was the complete defeat of the Uesugi forces and the Koga contingent. From that date the Go-Hà Âjà  ("Later-Hà Âjà Â") as they were called, went on to further triumphs, beginning with the destruction of the Uesugi family." Despite being vastly outnumbered, the Hà Âjà  army defeated the besiegers because, under Ujiyasu's orders, they were not bulked down by heavy armor and were not slowed by seeking to take heads.
This victory marked the decisive turning point in the struggle for the Kanto, and in the following years, proved the end of the à Âgigayatsu Uesugi line and destroyed the prestige of Uesugi Norimasa of the Yamanouchi Uesugi clan as Kantà  kanrei (Governor-General of Kantà  region, ). As a result, many of the Kantà  warlords became vassals of the Hà Âjà  clan.
In 1551, Ujiyasu defeated Uesugi Norimasa at Hirai Castle () and forced him to flee to Echigo, where he was taken into the protective custody of his retainer Nagao Kagetora, the later day Uesugi Kenshin and heir to Norimasa by adoption.
In 1559, Ujiyasu retired at the age of 45 and Hà Âjà  Ujimasa inherited formal leadership of the family.
In 1561, Kenshin assumed the post of Kantà  kanrei from Uesugi Norimasa and in the same year tried to conquer the region once more. Kenshin besieged Odawara Castle and burned down the town, withdrawing after two months (Siege of Odawara (1561)).
In 1561, after Uesugi withdrew from Odawara, the Hojo clan seized Iwatsuki Castle against à Âta Sukemasa and almost conquered whole Musashi Province.
In 1563, Ujiyasu allied himself with Takeda Shingen and regained Matsuyama Castle (æ¾山åÂÂ) in Musashi Province against Uesugi Norikatsu (ä¸ÂæÂÂæ²åÂÂ) (Siege of Musashi-Matsuyama (1563)).
In 1564, he took Kà Ânodai in Shimà Âsa Province following a battle against Satomi Yoshihiro (éÂÂ覠義å¼Â) (Battle of Kà Ânodai (1564)). Following this victory, Ujiyasu pushed on into Shimosa Province and Kazusa Province, but was never able to destroy the Satomi clan, who remained a thorn in the Hôjô's side right up until 1590.
Ujiyasu expanded the Hà Âjà  territory, which now covered five provinces (Sagami, Izu, Musashi, Shimosa and Kazusa), and managed and maintained what his father and grandfather had held.
After the second battle of Konodai in 1564, the Hà Âjà  largely contented themselves with ruling the vast tracts of land earned through 60 years of war and toil.
Ujiyasu's eastern moves brought the Hà Âjà  into conflict against the Satake clan of Hitachi Province. At the Battle of Numajiri in 1567, Satake Yoshishige defeated the Hojo forces and limited their expansion.
Towards the end of his life Ujiyasu saw the first major conflicts between his own clan and Takeda Shingen (æ¦ç° ä¿¡çÂÂ), who would become one of the greatest warlords of the period.
In 1568, in response to Hà Âjà Â's intervention into his invasion of Suruga Province, Shingen came into Musashi Province from his home province of Kai, attacking Hachigata (é¢形åÂÂ) (Siege of Hachigata (1568)) and Takiyama (æ»Âå±±åÂÂ) Castles, where Ujiyasu's sons repulsed them.
In 1569, after failing to take the two castles, Shingen nevertheless pressed on to the Hà Âjà Â's home castle of Odawara, burning the castle town and withdrawing after three days (Siege of Odawara (1569)). As the forces of Shingen withdrew from repeated failed sieges of Odawara Castle, two of Ujiyasu's seven sons, the brothers Ujiteru and Ujikuni, attacked him in the pass of Mimase (Battle of Mimasetoge), ending the first of the Takeda campaigns against the Hà Âjà  at Sagami province.
Later in the year, Shingen's son and future successor Takeda Katsuyori (æ¦ç° Ã¥ÂÂé ¼) led a successful siege against the Hojo Kanbara Castle (è²åÂÂÃ¥ÂÂ) in Suruga province (Siege of Kanbara).
Takeda Shingen also laid siege to other Hà Âjà  holdings in the surrounding provinces, including Fukazawa castle (深沢åÂÂ) in Suruga province which was taken in 1571 (Siege of Fukazawa).
Subsequently, Ujiyasu managed to make peace with Uesugi Kenshin and Takeda Shingen, the most powerful adversaries of Hà Âjà  Ujiyasu, letting his seventh son Hà Âjà  Saburà  be adopted by childless Kenshin and accepting the fait accompli of Shingen's reign over Suruga. To cement the ties of Takeda-Imagawa-Hojo, Ujiyasu also gave his two daughters to those two clans; Lady Hayakawa wed to Imagawa Ujizane, while Lady Hojo (Hojo Masako) wed to Takeda Katsuyori becoming his second wife. Ujiyasu died in 1571, passing on the Hà Âjà  domains to his eldest son Ujimasa (Ã¥ÂÂæ¡ æ°Âæ¿) in a relatively favourable situation.