end, and to provide more professional military leadership, Diocletian separated military from civil command at the lowest, provincial level. Governors of provinces on the frontiers were stripped of command of the troops stationed there in favour of purely military officers called duces limitis ("border commanders"). Some 20 duces may have been created under Diocletian. Most duces were given command of forces in a single province, but a few controlled more than one province e.g. the dux Pannoniae I et Norici. However, at higher echelons, military and administrative command remained united in the vicarii and praefecti praetorio. In addition, Diocletian completed the exclusion of the senatorial class, still dominated by the Italian aristocracy, from all senior military commands and from all top administrative posts except in Italy. Manpower To ensure the army received sufficient recruits, Diocletian appears to have instituted systematic annual conscription of Roman citizens for the first time since the days of the Roman Republic. In addition, he was probably responsible for the decree, first recorded in 313, compelling the sons of serving soldiers and veterans to enlist. Under Diocletian, the number of legions, and probably of other units, more than doubled. But it is unlikely that overall army size increased nearly as much, since unit strengths appear to have been reduced, in some cases drastically e.g. new legions raised by Diocletian appear to have numbered just 1,000 men, compared to the establishment of c. 5,500 in the Principate i.e. the new legions may have increased overall legionary numbers by only c. 15%. Even so, scholars generally agree that Diocletian increased army numbers substantially, by at least 33%. Supplies Diocletian's primary concern was to place the provision of food supplies to the army on a rational and sustainable basis. To this end, the emperor put an end to the arbitrary exaction of food levies (indictiones) for the army, whose burden fell mainly on border provinces and which had ruined them economically. He instituted a system of regular annual indictiones ("tax levies") with the tax demanded set in advance for 5 years and related to the amount of cultivated land in each province, backed by a thorough empire-wide census of land, peasants and livestock. To deal with the problem of rural depopulation in some areas (and consequent loss of food production), he decreed that peasants, who had always been free to leave their land during the Principate, must never leave