The most plausible theory of the constitution ascribed to Servius Tullius is that it was imposed by Etruscan conquerors. The earlier Romans had been quasi-sacerdotally ruled by priest-kings of the primitive type, "kings of the sacrifice," whose religious powers were balanced by the secular interest of the patrician heads of families--themselves priests of their family cults. The "Servian" constitution put down the _rex sacrificulus_, divided the city into four tribes, and its territory into twenty-six districts, each under a headman or headmen. The city at the same time was in part new walled, and the seven hills united; while the mass of the free population were divided into five classes according to their property, and enrolled for military purposes in 193 "centuries." In the first and richest class were forty centuries of men above forty-six for the defence of the city, and forty of younger men for service in the field; while the second, third, and fourth classes were divided into twenty centuries each, and the fifth class into thirty. The poorest of all were grouped in a separate century, the "Proletarians," or "breeders," without military duties; and the trumpeters, armourers, and carpenters in four more. New assemblies, the _comitia centuriata_, were formed, in which all members of the centuries shared, the old _comitia curiata_ being thus virtually superseded. The military organisation was made the basis of a fiscal one, in which the classes were taxed on the capital value of their property. As freedom from direct taxation was the mark of the ancient "free" communities in general, the whole arrangement seems to be one that only a conqueror could have imposed; and the tradition ran that Servius was regarded as the friend of the poor, who made his birthday an annual festival.