In historiography, the Western Roman Empire consists of the western provinces of the Roman Empire at any one time during which they were administered by a separate independent Imperial court, coequal with (or only nominally subordinate to) that administering the eastern half. Both "Western Roman Empire" and "Eastern Roman Empire" (or "Byzantine Empire") are modern terms describing de facto independent entities; however, at no point did Romans consider the Empire split into two, but rather considered it a single state governed by two separate Imperial courts out of administrative expediency. The view that the Empire was impossible to govern by one emperor was established by Diocletian following the disastrous civil wars and disintegration of the Crisis of the 3rd century, and was instituted