Historicalscholarship in postwar Japan has exhibited a renewed interest in the origins of dynastic rule in Yamato, and the process leading to the establishment of the Yamato rulers as sovereigns of an imperial polity in the seventh century. New theories of dynastic origins have led to new controversies, and many of the most basic assuptions of prewar historians are now being abandoned. Among these, the previously sacrosanct idea of unbroken dynastic continuity, usually expressed by the slogan bansei ikkei, has been effectively challenged. This idea, an important element of state ritual from the seventh century onward, does not antedate that century. It follows that during the previous three hundred years, which witnessed the successive establishment of at least three different dynastic regimes in Yamato, the prevailing political structures and ideologies differed radically from those represented in the traditional histories, which were not completed until the early eighth century. The bases of royal legitimacy and the nature of the kingship itself very probably changed drastically in the process of development.