In terms of regional jurisdiction there was no precise division between the four Tetrarchs, and this period did not see the Roman state actually split up into four distinct sub-empires. Each emperor had his zone of influence within the Roman Empire, but little more, mainly high command in a 'war theatre'. Each Tetrarch was himself often in the field, while delegating most of the administration to the hierarchic bureaucracy headed by his respective Praetorian Prefect, each supervising several Vicarii, the governors-general in charge of another new administrative level, the civil diocese. 