With the study of Japanese history progressed after the War, the view which regards Nara/early Heian period, during which the Ritsuryo system was the basis of governance, and mid-Heian/late Heian period, during which the Ritsuryo system was not necessarily the basis of governance, as separate periods became dominant.
戦後、日本史研究の進展に伴い、律令支配を原則としていた奈良期-平安前期と、律令を必ずしも支配原則としなくなった平安中期・後期とを別個の時代ととらえる考えが主流を占めていった。