This period of direct imperial rule was characterised by the effort to establish a centralised bureaucratic state in Japan patterned on the example offered by Tang dynasty China. The key instrument in this process was the adoption of law codes, known collectively as the ritsuryo (legal codes) system that established an elaborate hierarchy of offices headed by the emperor and prescribed the procedures of governmental administration at both national and provincial levels.

This period of direct imperial rule was characterised by the effort to establish a centralised bureaucratic state in Japan patterned on the example offered by Tang dynasty China. The key instrument in this process was the adoption of law codes, known collectively as the ritsuryo (legal codes) system that established an elaborate hierarchy of offices headed by the emperor and prescribed the procedures of governmental administration at both national and provincial levels.

However, the 9th century saw several efforts to personalise imperial rule by freeing it from the entrenched bureaucracy backfires, beginning a process in which the emperor was increasingly isolated from the machinery of government. This tendency was exacerbated by the creation or revival of two other extrabureaucratic posts to which the emperor delegated the authority he had formerly wielded personally: sessho (regent for an emperor still in his minority) and kampaku (regent for an adult emperor). From the late 9th century onward, members of the powerful Fujiwara family, who, while making no claim to the emperor’s title or ritual role, ruled in his name, dominated both posts.

The last century of the Heian period (794-1185) saw a waning of the power of the Fujiwara regents and a brief return of power to the imperial house. The leading figures through most this period, however, were not reigning emperors but retired sovereigns who retained headship of the imperial house after abdication.

Medieval Period (mid12th - 16th centuries)
Three more families, again nonimperial, held sway over the national government and the imperial institution from the closing years of the Heian period to the end of the Kamakura period (1185-1333) ushering in the age of warrior rule that was to last until the Restoration of 1868.

The first of these, the Taira family, ruled from Kyoto and legitimated themselves by occupying high offices within the imperial court. The second, the Minamoto family, destroyed the Taira in 1185 in a bloody war they waged from their base at Kamakura in eastern Japan. Remaining there after their victory, they established a wholly new pattern of national government, the Kamakura shogunate. The emperor remained in Kyoto and continued to preside over the imperial government, but these institutions were now reduced to almost complete impotence, real power devolving on the shogunate. Imperial legitimisation for this situation took the form of a commission from the emperor naming the head of the Minamoto family to the office of seii tai shogun, or "barbarian-subduing generalissimo", and thus by implication granting him absolute authority over territories and population beyond the reach of the much reduced imperial power.