The duties of the citizen are certain services which he owes to the state, which are paid either by his personal labour or by his property. The name for these duties (_moenera_, _munera_, connected with _munire_, to “fortify”) shows that they were connected with the military defence of the city. Originally most of such burdens were probably defrayed by the personal labour of the citizens.[530] Even the financial burdens which afterwards pressed on property (_munera patrimonii_) were largely defrayed by their enforced toil (_operae_).[531] In the municipal legislation of the close of the Republic we find the services of the citizens demanded for imposts such as the repair of roads and walls (_munitio_), which are in modern times covered by rates.[532] But the _tributum_, at whatever time it was first imposed, came to satisfy most of the necessities formerly met by this enforced labour. Other public needs were, in the Republic, met by contracts concluded by the censor, of which we shall speak in connexion with that office. A clear distinction could now be drawn between the great burden on property—the tribute—and the great burden on the person—military service.[533] The tribute was, from the time of the Servian census, imposed on the property which formed the basis of the _classes_—originally, therefore, on _res mancipi_;[534] later it was levied on all property and was paid by all registered citizens who were _sui juris_, the aes _hordearium_ and _equestre_ for the support of the knights being still paid by children and women who were also _sui juris_.[535] The lowest property taxed was, as we have seen, one of 1500 asses.[536] The taxation was not, however, like military service, graduated according to the _classes_, but was collected uniformly, usually at a rate of one _as_ in the 1000 (⅒ per cent). The tribute was an extraordinary tax and was imposed, like military service, only when the necessities of the state demanded it, practically when there was no reserve fund in the _aerarium_. The state regarded it as a loan rather than as its due, and sometimes considered itself bound, when its finances were more flourishing, to return the money to the contributors.[537] The vast revenues accruing to the state as a result of the third Macedonian war in 167 B.C. caused the cessation of the tribute,[538] and no further direct tax was collected at Rome until at the end of the third century A.D. it was reimposed by Diocletian and Maximian. Tribute was, indeed, inconsistent with Rome’s imperial position. It had been meant to defray the cost of the legions, but, with the creation of the empire, each province defrayed the expenses of its own military occupation.