The northern part of the region, and seemingly the center (including Tanba-gun and Tanba-go), was not included in Tanba Province but was instead separated to form Tango Province when the former was first established as one of the provinces administered by the Ryo-sei; this could be explained by the assumption that the central area of Tanba Province had been incorporated into the southern part of Tanba Province (a part of Tanba Province after the separation of Tango Province) from Tanba-gun in the north.
丹波国が令制国として成立した当初には、丹波郡・丹波郷を有して丹波国の中心であったとみられる北部の地域が丹波国として残されず、逆に丹後国として分離されてしまったのは、丹波国の中心が北部の丹波郡から、より都に近い丹波国南部（丹後分国後の丹波国の地域）へと移動していたためと考えられている。