What did the Kamakura bakufu (c. 1180-1333), Japan’s first so-called “warrior government” actually do? How did its “warrior” authority and role in governance change and expand over time? This dissertation examines the administration of the Kamakura bakufu through the its legal and administrative documents. It finds that these sources are critical to understanding how the warriors of the bakufu governed themselves, and to the process of expansion of “warrior” authority well beyond military matters. From 1199, the bakufu began to formalize and systemize its political, legislative, and judicial processes. By 1249, it had issued the List of Precedents on Judgment (Goseibai shikimoku), which outlined and standardized the basic principles of Kamakura justice in the vernacular, as well as 265 supplemental laws (tsuika-hō) to update and expand Kamakura policy. It had established new conciliar structures for governance and judgment, and added procedures and supporting organizations to increase the efficacy and reliability of the legal process as Kamakura’s jurisdiction expanded.

These sources show that the Kamakura bakufu consistently adapted to changing circumstances, taking on more authority and responsibilities as required by political exigency. This pattern of slow, uneven expansion further provides insight into the bakufu’s relationship with the imperial court and government. This dissertation argues that the bakufu operated as part of a “united state,” working as an (increasingly powerful) agency within the imperial government and under imperial authority. The bakufu actively worked to maintain the structures of the united state, and frequently reinforced the authority and jurisdiction of the imperial court and major religious institutions while limiting its own authority and the powers of its warriors. This arrangement allowed for the bakufu to continue to enjoy imperial legitimacy, and for undertaking sometimes substantial reforms without fundamentally altering or separating from the state. The bakufu was thus a complex and dynamic organization that resists easy categorization. It was not a separate or independent “warrior government,” nor merely one of several cooperative “powerful houses” (kenmon). The bakufu adapted and expanded to fill the space left by a retreating imperial court and provincial governments, drastically enlarging and refining its administration over time, changing to fit the needs of the moment. These findings further challenge the traditional conception of “warriors” as a distinct and separate social category, as well as the periodization and meaning of Japan’s “medieval” era. This work argues that overlooking the nature of the early development of the Kamakura bakufu obscures the broader development of “warrior” authority over the next 400 years, as the legal order originating under Kamakura became the basis for total warrior rule as later warrior administrations completely eclipsed the imperial government.