 Despite the prominence of the themes, it was some time before they became the basic unit of the imperial administrative system.Although they had become associated with specific regions by the early 8th century, it took until the end of the 8th century for the civil fiscal administration to begin being organized around them, instead of following the old provincial system.This process, resulting in unified control over both military and civil affairs of each theme by its "strategos", was complete by the mid-9th century, and is the "classical" thematic model mentioned in such works as the "Klētorologion" and the "De Administrando Imperio".