The was a Japanese samurai family who controlled the hereditary title of shikken (regent) of the Kamakura shogunate between 1203 and 1333. Despite the title, in practice the family wielded actual political power in Japan during this period compared to both the Kamakura shoguns, or the Imperial Court in Kyoto, whose authority was largely symbolic. The Hà Âjà  are known for fostering Zen Buddhism and for leading the successful opposition to the Mongol invasions of Japan. Resentment at Hà Âjà  rule eventually culminated in the overthrow of the clan and the establishment of the Ashikaga shogunate.
The Hà Âjà  are alleged to have been an offshoot of the Taira of the Kanmu branch, originating in Izu Province. On the other hand, modern theories question whether the Hà Âjà  clan was really descended from the Taira clan.
They gained power by supporting the defeat of the Taira by supporting the warlord Minamoto no Yoritomo in the Genpei War through both military assistance and by marriage to his blood relatives. Yet, when Yoritomo died eighteen years later, the Hà Âjà  usurped power from his family.
Hà Âjà  Tokimasa helped Minamoto no Yoritomo, a son-in-law, defeat the forces of the Taira to become Japan's first shà Âgun. Hà Âjà  Masako, Tokimasa's daughter, was married to Yoritomo. After the death of Yoritomo, Tokimasa appointed himself as shikken (regent) to the former shà Âguns young son, thus effectively transferring control of the shogunate to his clan permanently. Consequently, the shà Âguns became puppets and hostages of the Hà Âjà Â.
The Imperial court at Kyoto resented the decline in its authority during the Kamakura shogunate, while the clan, in turn, came to despise the weak Emperor Go-Toba. In 1221, the Jà Âkyà « War broke out between forces loyal to the recently retired Go-Toba and the second regent Hà Âjà  Yoshitoki. The Hà Âjà  forces easily won the war; the imperial court was brought under the direct control of the shogunate, while the emperor was exiled "to a remote island off western Japan." The shà Âguns constables were granted extensive civil powers, and the court was obliged to seek the shà Âguns approval for all of its actions. Although deprived of political power, the court was permitted to maintain its estates in Kyoto since it conveyed needed legitimacy on the otherwise unlawful rule of the shogunate.
Several significant administrative achievements were made during the Hà Âjà  regency. In 1225 the third regent, Hà Âjà  Yasutoki, established the Hyà Âjà Âsho (Council of State), which ended the threat of civil war by enabling potential rivals of the Hà Âjà  to share in the shogunate's decision-making and political power. The Hà Âjà  regent presided over the council, which was a successful form of collective leadership. The adoption of Japan's first military code of law â the Goseibai Shikimoku â in 1232 reflected the profound transition from an era of direct Imperial rule to the rule of the shà Âgun. While legal practices in Kyoto were still based on 500-year-old Confucian principles, the new code was a highly legalistic document that stressed the duties of stewards and constables, provided means for settling land disputes, and established rules governing inheritances. It was clear and concise, stipulated punishments for violators of its conditions, and remained in effect for the next 635 years.
Aside from the regents above, those who played an important role among the Hà Âjà  clan are: